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Mol. Cell. Biol., Dec 1995, 6670-6685, Vol 15, No. 12
A Gomez-Cuadrado, M Martin, M Noel and A Ruiz-Carrillo
Initiation binding repressor [corrected] (IBR) is a chicken erythrocyte
factor (apparent molecular mass, 70 to 73 kDa) that binds to the sequences
spanning the transcription initiation site of the histone h5 gene,
repressing its transcription. A variety of other cells, including
transformed erythroid precursors, do not have IBR but a factor referred to
as IBF (68 to 70 kDa) that recognizes the same IBR sites. We have cloned
the IBR cDNA and studied the relationship of IBR and IBF. IBR is a
503-amino-acid-long acidic protein which is 99.0% identical to the recently
reported human NRF-1/alpha-Pal factor and highly related to the
invertebrate transcription factors P3A2 and erected wing gene product
(EWG). We present evidence that IBR and IBF are most likely identical
proteins, differing in their degree of glycosylation. We have analyzed
several molecular aspects of IBR/F and shown that the factor associates as
stable homodimers and that the dimer is the relevant DNA- binding species.
The evolutionarily conserved N-terminal half of IBR/F harbors the
DNA-binding/dimerization domain (outer limits, 127 to 283), one or several
casein kinase II sites (37 to 67), and a bipartite nuclear localization
signal (89 to 106) which appears to be necessary for nuclear targeting.
Binding site selection revealed that the alternating RCGCRYGCGY consensus
constitutes high-affinity IBR/F binding sites and that the direct-repeat
palindrome TGCGCATGCGCA is the optimal site. A survey of genes potentially
regulated by this family of factors primarily revealed genes involved in
growth-related metabolism.
Copyright © 1995, American Society for Microbiology
Initiation binding repressor, a factor that binds to the transcription initiation site of the histone h5 gene, is a glycosylated member of a family of cell growth regulators [corrected] [published erratum appears in Mol Cell Biol 1996 Feb;16(2):735]
Cancer Research Center, Medical School of Laval University, L'Hotel- Dieu de Quebec, Canada.
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