The Gfi-1B Proto-oncoprotein represses p21WAF1 and inhibits myeloid cell differentiation

Item Type:	Article
Title:	The Gfi-1B Proto-oncoprotein represses p21WAF1 and inhibits myeloid cell differentiation
Creators Name:	Tong, B. and Grimes, H. and Yang, T.Y. and Bear, S. and Qin, Z. and Du, K. and El-Deiry, W. and Tsichlis, P.
Abstract:	Gfi-1 is a cellular proto-oncogene that was identified as a target of provirus integration in T-cell lymphoma lines selected for interleukin-2 (IL-2) independence in culture and in primary retrovirus-induced lymphomas. Gfi-1 encodes a zinc finger protein that functions as a transcriptional repressor. Here we show that Gfi-1B, a Gfi-1 related gene expressed in bone marrow and spleen, also encodes a transcriptional repressor. IL-6-induced G1 arrest and differentiation of the myelomonocytic cell line M1 were linked to the downregulation of Gfi-1B and the parallel induction of the cyclin-dependent kinase inhibitor p21WAF1. Experiments addressing the potential mechanism of the apparent coordinate regulation of these genes revealed that Gfi-1B represses p21WAF1 directly by binding to a high-affinity site at -1518 to -1530 in the p21WAF1 promoter. Forced expression of Gfi-1B, but not of Gfi-1B deletion mutants lacking the repressor domain, blocked the IL-6-mediated induction of p21WAF1 and inhibited G1 arrest and differentiation. We conclude that Gfi-1B is a direct repressor of the p21WAF1 promoter, the first such repressor identified to date, and that sustained expression of Gfi-1B blocks IL-6-induced G1 arrest and differentiation of M1 cells perhaps because it prevents p21WAF1 induction by IL-6.
Keywords:	3T3 Cells, Amino Acid Sequence, Amino Acid Sequence Homology, Bone Marrow Cells, Cell Differentiation, Cell Line, Cyclin-Dependent Kinase Inhibitor p21, Cyclins, Developmental Gene Expression Regulation, Genetic Epistasis, Genetic Promoter Regions, Hematopoietic Stem Cells, Interleukin-6, Molecular Sequence Data, Monocytes, Proto-Oncogene Proteins, Repressor Proteins, Spleen, Tissue Distribution, Zinc Fingers, Animals, Mice, Rats
Source:	Molecular and Cellular Biology
ISSN:	0270-7306
Publisher:	American Society for Microbiology
Volume:	18
Number:	5
Page Range:	2462-2473
Date:	May 1998
Official Publication:	http://mcb.asm.org/cgi/content/abstract/18/5/2462
PubMed:	View item in PubMed

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