Enhanced binding of poly(ADP-ribose)polymerase-1 and Ku80/70 to the ITGA2 promoter via an extended cytosine-adenosine repeat.
BACKGROUND
We have identified a cytosine-adenosine (CA) repeat length polymorphism in the 5'-regulatory region of the human integrin alpha2 gene ITGA2 that begins at -605. Our objective was to establish the contribution of this polymorphism to the regulation of integrin alpha2beta1 expression, which is known to vary several-fold among normal individuals, and to investigate the underlying mechanism(s).


RESULTS
In combination with the SNP C-52T, previously identified by us as a binding site for the transcription factor Sp1, four ITGA2 haplotypes can be distinguished, in the order in which they enhance ITGA2 transcription: (CA)(12)/-52C>(CA)(11)/-52C>(CA)(11)/-52T>(CA)(10)/-52T. By DNA affinity chromatography and chromatin immunoprecipitation (ChIP) assays, we show that poly (ADP-ribose)polymerase-1 (PARP-1) and Ku80/70 bind specifically and with enhanced affinity to the longer (CA)(12) repeat alleles.


CONCLUSIONS
The increased binding of PARP-1 and Ku80/70, known components of transcription co-activator complexes, to the longer (CA)(12) alleles of ITGA2 coincides with enhanced alpha2beta1 expression. The most likely explanation for these findings is that PARP-1 and Ku80/70 contribute to the transcriptional regulation of ITGA2. These observations provide new insight into the mechanisms(s) underlying haplotype-dependent variability in integrin alpha2beta1 expression in human platelets and other cells.
Cheli
Yann
Y
The Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, United States of America.
Williams
Shirley A
SA
Ballotti
Robert
R
Nugent
Diane J
DJ
Kunicki
Thomas J
TJ
D000241:Adenosine / Q000378:metabolism*; D002460:Cell Line; D002846:Chromatography, Affinity; D003596:Cytosine / Q000378:metabolism*; D006801:Humans; D039421:Integrin alpha2 / Q000235:genetics*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide; D011485:Protein Binding; D012091:Repetitive Sequences, Nucleic Acid
C056564:ITGA2B protein, human; D039421:Integrin alpha2; D003596:Cytosine; D011065:Poly(ADP-ribose) Polymerases; D000241:Adenosine