Download The gene for the human architectural

4262-4266
Nucleic Acids Research, 1995, Vol. 23, No. 21
© 1995 Oxford University Press
The gene for the human architectural transcription
factor HMGI-C consists of five exons each coding for
a distinct functional element
Kai-Yin Chau 2 , Umesh A. Patel1, Kam-Len D. Lee2, Hing-Yat P. Lam3 and
Colyn Crane-Robinson1*
1
Biophysics Laboratories, University of Portsmouth, Portsmouth P01 2DT, UK, department of Applied Biology
and Chemical Technology, Hong Kong Polytechnic University, Hong Kong and 3Department of Biochemistry,
Hong Kong University of Science and Technology, Hong Kong
Received August 25, 1995; Revised and Accepted September 25, 1995
ABSTRACT
The gene on chromosome 12 coding for the human
protein HMGI-C has been cloned and partially sequenced. It consists of five exons, the first and last of
which include long untranslated regions. The 5' UTR
Includes a (CA/T)n tract and a polymorphic (CT)n tract.
Exons II, III and IV (87,51 and 33 bp) are dispersed over
>30 kb. Exons Mil separately encode the three basic
DNA binding domains ('A-T hooks'), exon IV encodes
an 11 amino acid sequence characteristic of HMGI-C
and absent from the human HMGI(Y) gene [Friedmann.M., Holth.L.T, Zoghbi,H.Y. and Reeves.R. (1993)
Nucleic Acids Res., 21, 4259-1267], whilst exon V
encodes the acidic C-terminal domain, which is subject to multiple phosphorylation. The HMGI-C gene is
thus a striking example of the separation of functional
protein elements into different coding exons.
INTRODUCTION
The mammalian high mobility group (HMG) proteins consist of
three families, all implicated in transcriptional regulation. The
best understood functionally is the HMGI family, which consists
of three members: HMGI and HMGY are alternative splicings of
the same gene (1-3), HMGI having an additional 11 amino acids,
and HMGI-C, which is coded from a separate gene (4,5). The
HMGI proteins all contain -100 amino acids with a very low
proportion of large hydrophobics and they do not therefore fold
autonomously. They all contain three nine-residue basic DNA
binding domains (DBD, also refered to as 'A-T hooks') and a
highly acidic C-terminal domain of 15 amino acids that is the
location of multiple casein kinase II phosphorylation sites (6,7).
HMGI(Y) has been shown to participate in the assembly of
combinatorial protein complexes on the promoters of several
inducible genes and it can thus be regarded as an architectural
component. Prominent among these is the human interferon-fj
(IFN-P) promoter, at which I(Y) cooperates with both NFKB and
* To whom correspondence should be addressed
GenBank accession nos L41044, L44578 and L46353
the bZIP protein ATF2 to mediate viral induction of the gene (8).
At the human E-selectin promoter I(Y) mediates the interaction
of two NFicB-containing complexes essential for cytokineinduced expression (9), whilst at the IL4 promoter I(Y) can have
a suppressive effect (10). Recently it has been shown that I(Y)
also interacts specifically with the POU domain of the Tst-1 /Oct-6
protein to activate expression of JC viral genes in infected glial
cells (11). The close structural homology between I-C and I(Y)
implies that I-C is also a component of combinatorial promoters
and this is emphasized by the finding that serum stimulation of
quiescent 3T3 cells leads to expression of delayed early response
(DER) genes, in particular HMGI-C and HMGI(Y) (12). No
target gene or interacting protein partner has yet been defined for
HMGI-C.
The HMGI proteins are not observed at significant levels in
differentiated adult tissues, but expression is induced in proliferating and transformed cells. Rat thyroid cells express high levels
of all three proteins following transformation with a variety of
oncogenes and a correlation is observed between the level of
expression and the degree of neoplastic transformation (13,14).
This is particularly evident for HMGI-C, which is abundant only
in the most transformed cells. The relationship between levels of
HMGI proteins and the process of transformation/proliferation
has been emphasized by the finding that expression of antisense
I-C is able to reverse neoplastic transformation induced in rat
thyroid cells by retroviruses (15). The tissue specificity of
HMGI-C expression in transformed human cells appears more
restricted than in rodent cells. Whereas high levels of I-C have
been observed in mouse 3T3 cells, Lewis lung carcinomas and
lymphomas (16,17), as well as in transformed rat thyroid cells
(13), the human protein has so far been observed only in
hepatoma cells and is essentially absent from HeLa and from a
variety of hemopoietic cells (5).
In order to better understand the involvement of HMGI family
proteins, particularly I-C, in cell proliferation we have cloned the
cDNA for mouse and human I-C (4,5). This demonstrated firstly
that the peptidic segments separating the highly conserved DBDs
of I-C are of similar composition to those of I(Y), but of quite
Nucleic Acids Research, 1995, Vol. 23, No. 21 4263
The Human HMGI-C Gene and Its cDNA
ATG
1185 bp
TAG
1922 bp
1005 bp
100 bp
7
*--..,3'bTR/
Exons I 2- 6 II
coding sequences 108 bp 87 bp
10 3
-
III
51 bp
-12.8
IV
33 bp
cDNA
2Kb
V
45 bp
Genomic Map
kb
sequenced regions
\
G21
n
i
EcoR1
HlndBI
C2
G52
231
X. Clones
Figure 1. The organization of the human HMGI-C gene on chromosome 12 and its relationship to the expressed cDNA. Two possible termination sites in the 3' UTR
are shown at 1922 and 2927 bp downstream of the TAG stop codon.
different sequence, and, secondly, that I-C contains an additional
domain of 11 amino acids between the third DBD and the acidic
C-terminal domain. The present work describes the genomic
cloning and sequencing of the single functional human HMGI-C
gene, which reveals a simple correlation between the coding
exons and the functional elements of the protein. Sequences also
obtained for 1755 bp upstream of the transcriptional start should
in the future permit a functional analysis of the mechanisms
controlling the developmental- and tissue-specific expression of
HMGI-C.
MATERIALS AND METHODS
Screening of human genomic libraries
Plaques (1 x 106) from a A.GEM-11 human lymphocyte genomic
library (Novagen) were screened by hybridization in QuickHyb
solution (Stratagene) using a Megaprime Kit (Amersham) to label
a 224 bp cDNA fragment (HC29; 5) as probe. Four clones were
isolated whichremainedpositive after tertiary screening. The two
longest overlapping clones (G21 and G52) were further characterized by restriction mapping and Southern blot analysis.
Another 1 x 106 plaques from a XEMBL3 human lymphocyte
genomic library (Clontech) were screened as above with a 218 bp
cDNA probe from the 3'-end of the cDNA. Out of five clones
which remained positive after tertiary screening, the two longest
overlapping clones (231 and C2) were further characterized as
above.
DNA sequencing
Genomic clones in X vectors were digested with the appropriate
restriction enzymes, subcloned into the BlueScript II (KS+)
vector (Stratagene) and transformed into Escherichia coli JM109.
A series of nested deletions were generated using the doublestranded Nested Deletion Kit (Pharmacia). Both strands of the
genomic subclones were sequenced using a Toyobo ATth
Sequencing Pro Kit (Cambridge BioScience) and the image
captured by a Phosphorimager (Molecular Dynamics) or automatically sequenced using an ALF DNA Sequencer (Pharmacia).
DNASTAR and DNASIS programs were used for sequence data
analysis.
Primer extension
A 21mer oligonucleotide (100 ng) corresponding to the antisense
strand of the HMGI-C sequence shown in bold in the 5' UTR (Fig.
2) was 5'-end-labelled with 32P using polynucleotide kinase. An
aliquot of 10 ng (~5 x 106 c.p.m.) of this labelled primer was
incubated with 20 (ig total human hepatoma RNA extracted from
PLC/PRF/5 cells in 30 ul hybridization solution (80% formamide, 20 mM Tris-HCl, pH 7.5,400 mM NaCl, 1 mM EDTA) at
85°C for 10 min and then at 30°C for 10 h. The RNA with the
annealed primer was ethanol precipitated and resuspended in
buffer containing 50 mM Tris-HCl, pH 8.3, 75 mM KC1, 3 mM
MgCl2,10 mM dithiothreitol, 5 mM dNTP, 50 ng/ml actinomycin
D, 1 U/(il RNasin ribonuclease inhibitor (Promega), 10 (iCi
[a-32P]dCTP (3000 Ci/mmol; ICN) and 400 U M-MLV reverse
transcriptase (BRL). The extension reaction was carried out at
42°C for 1 h and stopped with the addition of EDTA to 25 mM.
Sonicated salmon sperm DNA (10 (ig) and DNase-free RNase A
(2 \ig) were added and incubated at 37°C for 15 min. The solution
was extracted with phenol/chloroform, ethanol precipitated,
resuspended in sequencing stop buffer, denatured and run on a
sequencing gel.
RESULTS
Genomic structure of the HMGI-C gene
The human HMGI-C gene is >36 kb in length, of which >19 kb
is fully sequenced and contains five exons (Fig. 1). Exon I
contains 1185 bp of 5' UTR, the ATG initiation codon and the
N-terminal sequence coding for amino acids 1-36, which include
thefirstbasic DNA binding domain (DBD 1) of nine amino acids.
The first intron is 2577 bp in length. Exon II encodes amino acids
4264 Nucleic Acids Research, 1995, Vol. 23, No. 21
ccGAGGCGGAGCocg. . . . 183 bp .. . .caa£tgc.... 46 bp ... .agcccgggmtcctgtccctttaacc
S
156 bp ... . cgc§_«cc.... 77 bp ... .acgcacacacaccacacacactcacactcacacacact
cc...
cacacacactcatcc.... 249 bp ... . aatctcttctctctctctctctctctqtctctctctctctctctctc
M S A R O E
t c t c t c t c t c t c t c t c t c g c . • • • 475 bp . . . .gcggtagcggcggcgggaggcaggAXOJUJCaCACGCGOTOJU}
O
A
Q
Q
P
S
T
S
A
R K Q Q Q
AOOAAOCAGCAGCAAgtcagtacga
Q
S
Q
P
A
A
intron I
2 . 6 kb
P
A
P
Q
K
R
intron II
1 0 . 3 kb
R
O
R
P
K P T O E P
tcacaattagOAACCAACCOGTQAOCCC
S P K R P R O R P K S S K B K S P S K A A
TCTCCTAA0AaACOlAGGGGAAflACCCAAAG<XiAGCAAAAACAAaAOTCCCTCTAAA
C
O
Q
K
K A I A T Q I K R P R Q R P R K
tcatttgcagAAAOCAOlUUKXACTOQAaAAAAACOOCCAAaAOOCAOACCTAOOAAA
H
intron III
P Q Q V V Q K K P A Q
TGOgtgagtaata. . . . >6 kb . . . tcctccttagCCACAACAAOTTOTTCJUJAAOAAOCCTOCTCAOgtaagaca
ta...
i n t r o n IV
E E T K 1 T S S Q K 8 A E 1 D *
- 1 2 . 8 kb . . . gtgtgttcCagOAOaAAACTGAAOAaACATCCTCACAAaAOTCTOCCOAAOAOaACTAOg
gg....
103 bp • •••tctqqqqtqqqqtqqqqtgqqqtqqqqqaqqqggqqqtggqqtqqqqaqaa.... 1678
bp
t a a a a t a a a . . • • 78 bp . . . . t o t o t t t t t a a • . . . 962 bp • . • . c a o a a t a a a
. . . . 2 3 bp
. . . . t<rt<rttttg«t • . • . 30 bp . . . . m t i i t M l . . . . 88 bp • • • . t g t g t t t t a c a . • • . 753 bp
ttc
Figure 2. Partial sequence data for the human HMGI-C gene. In the 5' UTR the cytosine marked with an asterisk * represents the transcriptional start established by
extension from a primer complementary to the sequence shown 52 bp downstream in bold. The adenine marked by a § represents the 5'-limit of cDNA sequence
established from cDNA library probing. The CA and CT repeats are underlined. The GC box at the 5'-end is shown in upper case. In the 3' UTR the GGGGT repeats
are underlined. Three pairs of AATAAA/TGTGTTTT polyadenylation signal sequence/termination sequence are underlined in bold. The final 3' cytosine is 3832 bp
downstream of the TAG stop codon.
37-65, which include the second basic DNA binding domain
(DBD 2), followed by the second intron of 10336 bp. Exon III
encodes amino acids 66-82, which include the third basic DNA
binding domain (DBD 3) and finishes with W82. The third intron
is of unknown length and is followed by exon IV, which is very
short and encodes amino acids 83-93 (PQQVVQKKPAQ). This
undecapeptide separates DBD 3 from the C-terminal acidic
domain (amino acids 94-108). This last domain, plus the TAG
stop codon, is coded for in exon V, together with 2927 bp of 3'
UTR. Sequencing of genomic fragments containing all of the
exons shows the coding sequences to be identical to those of the
cloned cDNA (5), implying that the functional gene has been
cloned. Southern blot analysis of genomic DNA using a cDNA
probe covering all the coding sequences showed the presence of
each exon on a different restriction fragment (data not shown),
also demonstrating the existence of only one gene, i.e. the absence
of any pseudogenes. This is in marked contrast to the situation for
human HMGI(Y), for which the existence of several pseudogenes
has been noted (1).
Figure 2 shows some of the HMGI-C gene sequence data
obtained. All the exon-intron boundaries conform to the consensus
splice donor-acceptor sequences, including the GT-AG motif (18).
Since the poly(A) addition site(s) is unknown, the 3' UTR was fully
sequenced. There are three possible AATAAA polyadenylation
signal sequences having an associated TGTGTTTT termination
sequence a short distance downstream (underlined/bold in Fig. 2).
The second of the three has a spacer of 23 bp between the two
sequences, which conforms to the requirement for <50 bp
between a signal sequence AATAAA and the consensus termination sequence YGTGTTYY (Y = C or T) for efficient formation
of a 3'-terminus in mammalian mRNAs (19). The most 5'
AATAAA signal has a spacer of 78 bp to the associated consensus
termination sequence and the most 3' has a spacer of 88 bp, both
of which might be functional. There are six other AATAAA
sequences downstream of the TAG termination codon, but none
have an associated consensus termination sequence.
Transcriptional start
In the cDNA clone already described (5) 812 bp of the 5' UTR
were sequenced. A primer complementary to a sequence close to
this 5'-end was therefore used to generate further cDNA clones,
using as before total RNA from the human hepatoma cell line
PLC/PRF/5 as template. In this manner three identical clones
were recovered that gave an additional 135 bp of upstream cDNA
sequence, making a total of 947 bp. This limit is indicated by a §
in Figure 2. Since there is a highly GC-rich region just upstream
of this point, a full-length 5' UTR was probably not cloned by this
approach. 5'-RACE experiments were unable to give any more
upstream cDNA sequence. Primer extension was therefore used
Nucleic Acids Research, 1995, Vol. 23, No. 21 4265
EXON
HMGI-C
HMGHY)
Sta»(bp)
1
II
III
IV
V
1296
87
51
33
2875
179
84
51
_
1397
INTRON
HMGt-C
HMGim
Slze(kb)
V
VI
VII
1
D
III
IV
1.8
0.7
1.3
_
zsn
11X336
-12.8
VIII
-ExonI
DBD1
— Exon 11"
DBD2
-ExonV
* — Exon m—•> • C x o n l V *
DBDS
1
(M) mmucruugaHii
)
e
I
I
1I
10
20
30
40 J
50
20
1
10
— - — REPRESENT THE 3 BASIC DNA BINDING DOMAINS (DBD)
gun
]„
•• 11 iiiiiimiiiiiii
f
i
t
mil
90
I l l l l i n C - TERMINAL ACIDIC DOMAIN (SITES OF PHOSPHORYLATION)
S/TPXKK POTENTIAL cdc2 PHOSPHORYLATION SITES ARE UNDERUNED & OVERUNED
Figure 3. Comparison of the human HMGI-C and HMGI( Y) genes (1). The upper part compares exon and intron sizes and the lower part illustrates the equivalence
of the intron insertion points (vertical arrows) in the two genes. The numbering refers to the HMGI protein sequence
with a primer complementary to the genomic sequence in bold
located just upstream of § in Figure 2. This experiment (data not
shown) indicated only a single transcriptional start site at a
cytosine indicated by * in Figure 2.
Northern blot analysis using total RNA prepared from PLC7
PRF/5 cells showed an abundant transcript of -3.8 kb and a
second longer transcript of -4.5 kb at lower levels (data not
shown). Addition of 1185 bp of 5' UTR (from the cytosine
defined by primer extension) to 330 bp of coding DNA (including
the ATG and TAG codons) and 2927 bp of 3' UTR (to the second
termination sequence) accounts for a total of 4442 bp; this is close
to the 4.5 kb size estimated for the longer transcript. If the more
upstream termination sequence were used in conjunction with the
same 5' start site, a transcript of 3437 bp would result.
The whole of the sequenced 2.9 kb upstream of the initiating
ATG was scanned for consensus promoter elements. A GC box
with a perfect match was located -200 bp upstream of the
transcriptional start site (upper case in Fig. 2), but no associated
TATA box was found.
Characterization of repeated sequences
An interesting feature of the 5' UTR in the previously reported
cDNA sequence (5) is a continuous tract of (CT}i% interrupted by
a single GT and omission of a single C. Genomic clones in this
region from the two lymphocyte libraries indicated the presence
of polymorphism. A placental genomic library was therefore
screened with cDNA clone HC29 and this region of the 5' UTR
sequenced. Clone gDNA3, isolated from the placentaJ library, has
(CT)27 and omission of the GT. The two clones from the
lymphocyte libraries show differences with respect to each other
as well as to gDNA3: clone gDNA 1 has (CT)29, but is interrupted
by the GT at a different position; clone gDNA2 shows (CT)24 and
the GT is omitted. All three clones show omission of the single
C. The 5' UTR also has arepeatof (CA) )9 interrupted by four CTs
and a single C (Fig. 2). The 3' UTR has a 4-fold tandemrepeatof
the pentanucleotide GGGGT followed by nine Gs interrupted by
a single A and then two more tandem GGGGT repeats
(underlined in Fig. 2). These repeats and the polymorphic region
could be important for regulatory functions.
DISCUSSION
Organization of the HMGI-C gene and comparison with
the I(Y) gene
The HMGI-C gene is substantially longer (>36 kb) than the I(Y)
gene (1), since the latter is only -10 kb in length, despite the
proteins being of similar size (20,2,4,5). The mRNA lengths are
greater for I-C, at 4.5/3.8 kb as compared with -1.85 kb for I(Y)
(20), due to both the 5' and 3' UTRs being longer for I-C. The
human HMGI-C gene comprises five exons (Fig. 1), with exon
I being 71% G+C and equally rich in CpG as in GpC. This
GC-rich region finishes -1 kb into intron I, after which the CpG
density is only one third that of GpC. We conclude that this
tissue-specific gene has a CpG island (21). The most striking
feature of the I-C gene is that each exon codes for a distinct
functional element. Each of the three DBDs (previously refered
to as 'A-T hooks'), shown to bind to the narrow minor groove of
A-T rich DNA, (22,23) is located on a separate exon (l-III), as is
the C-terminal acidic domain (exon V). Comparison with the
human gene for HMGI(Y) is particularly interesting (see Fig. 3)
in that the intron insertion positions are at functionally identical
points in the sequence. Exons I—III of I-C correspond to exons
V-VII of I(Y), the difference in numbering resulting from the
multiple non-coding upstream exons in the I(Y) gene (1).
Particularly interesting is the observation that the 11 amino acid
sequence unique to HMGI-C and absent from I(Y) is coded by a
separate exon (IV). The HMGI-C gene is thus a striking example
of individual exons representing separated structural/functional
elements of the protein. It has already been suggested (1) that the
DBDs evolved from a common ancestral genomic sequence.
Equally, the I-C and I(Y) genes as a whole may have a common
ancestor. In the case of I-C an additional exon (IV) has been
acquired and in the case of HMGI alternative splicing gives rise
to the HMGY variant lacking an 11 amino acid segment between
DBDs 1 and 2 that is also absent from HMGI-C.
4266 Nucleic Acids Research, 1995, Vol. 23, No. 21
Whilst this manuscript was in preparation two papers appeared
describing translocations within the HMGI-C gene assumed to be
causative in the development of lipomas, which are benign
mesenchymal neoplasms (24,25). It has been known for some
time that translocations on the long arm of chromosome 12 are
frequently involved in lipoma formation (26) and it was shown
by 3'-RACE (24,25) that in a significant proportion of cases the
break point in the I-C gene is at the junction of exon III (W82) and
the following intron, leading to in-frame fusion to a number of
other sequences, e.g. serine/threonine-rich acidic domains and
LIM domains. Such chimeric proteins would retain the DNA
binding properties of HMGI-C, lack its most individual characteristic conferred by the exon IV coding sequence and acquire
potentially new transcriptional regulatory domains. Loss of the
acidic C-terminal domain from I-C would rob the chimeric protein
of the native sites of phosphorylation and presumably therefore of
critical regulatory mechanisms. The consequence could be the
deregulation of HMGI-C target genes (presently undefined). As a
parallel example the case of translocations to the MLL gene on
chromosome 11 in childhood acute leukaemias can be cited. The
MLL protein contains three DBDs ('A-T hooks') near its
N-terminus having sequences similar to those of the HMGI
proteins and all containing the core tetrapeptide RGRP (27).
Together with a DNA methyltransferase domain, these become
fused to most of the serine/proline-rich ENL protein from
chromosome 19. The resulting chimeric protein, having lost the
sequence-specific zinc fingers of MLL, may have a broadened
spectrum of transcriptional activation.
The third intron in the HMGI-C gene is >6 kb in length from
our observations and was found to be -140 kb from the cosmid
mapping of Schoenmakers et al. (25). Its exceptional length may
be related to its frequent involvement in translocations. Certainly,
the fact that the exons of the HMGI-C gene correspond to separate
functional elements in the native protein must predispose the gene
to the formation of chimeric sequences coding for proteins with
the capability of novel, albeit aberrant, functions as transcriptional activators or repressors. Ashar et al. (24) also reported that
homozygous disruption of the HMGI-C gene in mice leads to the
pygmy phenotype (28,29), characterized by less body fat than
wild-type mice. It will therefore be of considerable interest to
analyse promoter functions in the 5' region of the HMGI-C gene
so as to define itsregulation,particularly during adipogenesis and
mesenchymal differentiation.
ACKNOWLEDGEMENTS
K-Y. C. acknowledges the award of a studentship by the Hong
Kong Polytechnic University. Financial support from the EC
SCIENCE Programme (CT91 -0619) is gratefully acknowledged.
REFERENCES
1 Friedmannjvl., HolthJL.T., Zoghbi,H.Y. and ReevesJ*. (1993) Nucleic
Acids Res., 21,4259-4267.
2 Eckner.R. and BimstieUvI.L. (1989) Nucleic Acids Res., 17, 5947-5959.
3 Johnson.K.R., LehnJXA. and Reeves.R. (1989) Mol.Cell. Biol., 9,
2114-2123.
4 Manfioletti.C, Giancotti.V., BandieraA., Buratti.E., Sautiere.P., CaryJ1.,
Crane-Robinson.C, Coles.B and Goodwin.G.H. (1991) Nucleic Acids
Res., 19, 6793-6797.
5 Patel.UA, BandieraA., ManfioletU.G., Giancotti.V., Chau,K.-Y. and
Crane-Robinson.C. (1994) Biochem. Biophys. Res. Commun., 201, 63-70.
6 Ferranti,R, MalomiA, Marino.G., Pucci.P., Goodwin.G.H., Manfioleni.G.
and Giancotti.V. (1992) / Biol. Chem., 267, 22486-22489.
7 Hcath.C. (1995) PhD Thesis, London University.
8 Thanos.D. and Maniatis.T. (1992) Cell, 71, 777-789.
9 Lewis.H., Kaszubska,W., DeLamarterJ.F. and WhelanJ. (1994) Mol. Cell.
Biol., 14, 5701-5709.
10 Chuvpilo.S., Schomberg.C, Gerwig,R., HeinflingA. Reeves.R.,
Grummt,F. and Serfling.E. (1993) Nucleic Acids Res., 21, 5694-5704.
11 Leger,R, Sock,E., Renner.K., Grummt,F. and Wegnerjvl. (1995) Mol. Cell.
Biol., 15, 3738-3747.
12 LanahanA, WilliamsJ.B., Sanders.L.K. and Nathans.D. (1992) Mol. Cell.
Biol., 12, 3919-3929.
13 Giancotti.V., BerlingicriJvl.T., DiFioreJ'.P., FuscoA, Vecchio.G. and
Crane-Robinson,C. (1985) Cancer Res., 45, 6051-6057.
14 Giancotti.V., Pani.B., D'Andrea,P., Berlingieri,M.T., Di Fiore.P.P..
FuscoA, Vecchio.G., Phrlp.R., Cranc-Robinson.C, Nicolas.R.H.,
Wright,C.A. and Goodwin.G.H. (1987) EMBOJ., 6, 1981-1987.
15 BerlingieriJvl.T., Manfioletti.G., Santorojvt, BandieraA., Visconti.R.,
Giancotti/V. and FuscoA (1995) Mol. Cell. Biol., 15, 1545-1553.
16 Giancotti.V., Buratti,E., Perissin.L., Zorzet.S., BalmainA, Portella,G.,
FuscoA and Goodwin.G.H. (1989) Exp. Cell. Res., 184, 538-545.
17 Giancotti.V., BandieraA.. Ciani.L., Santoro.D., Crane-Robinson.C,
Goodwin.G.H., Boiocchijvl., Dolcetti.R. and Casetta,B. (1993) Eur. J.
Biochem., 213, 825-832.
18 Breathnach,R. and Chambon.P. (1981) Annu. Rev. Biochem., 50, 349-383.
19 McLauchlandJ., GafTney.D., WhittonJ.L. and ClementsJ.B. (1985)
Nucleic Acids Res., 13, 1347-1368.
20 Johnson.K.R., Lehn.DA, Elton.T.S., Barr.PJ. and Reeves.R. (1988) J.
Biol. Chem., 263, 18338-18342.
21 BirdAP. (1986) Nature, 321, 209-213.
22 Reeves.R. and NissenJvl.S. (1990) J. Biol. Chem., 265, 8573-8582.
23 Geierstanger,B.H., Volkman.B.F., Krcmer.W. and Wemmer.D.E. (1994)
Biochemistry, 33, 5347-5355.
24 Ashar.H.R., Schoenberg Fejzo.M., Tkachenko.A., Zhou,X., FletcherJ A ,
Wercmovicz^., Morton.C.C. and Chada,K. (1995) Cell, 82, 57-65.
25 Schoenmakers,E.F.P.M., Wanschura,S., Mols.R., BullerdiekJ., Van den
Berghe.H. and Van de Ven.WJ.M. (1995) Nature Genet., 10,436-444.
26 Sreekantaiah.C, Leong.S.P.L., Karakousis.C.P., McGee,D.L.,
Rappaport,W.D., Villar.H.V, NealA. Fleming.S., WankelA,
Herrington.P.N., CarmonaJ*. and SandbergA (1991) Cancer Res., 51,
422-433.
27 TkachukJD.C, Kohler.S. and aearyJvl.L. (1992) Cell, 71, 691-700.
28 Xiang,X., Benson.K.F. and Chada,K. (1990) Science, 247, 967-969.
29 Benson,K.F. and Chada,K. (1994) Genet. Res. Camb., 64, 27-33.