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Báo cáo khoa học: The Drosophila homeodomain transcription factor, Vnd, associates with a variety of co-factors, is extensively phosphorylated and forms multiple complexes in embryos

Vnd is a dual transcriptional regulator that is essential forDrosophila dor-sal–ventral patterning. Yet, our understanding of the biochemical basis for its regulatory activity is limited. Consistent with Vnd’s ability to repress target expression in embryos, endogenously expressed Vnd physically asso-ciates with the co-repressor, Groucho, inDrosophilaKc167 cells. | ễFEBS Journal The Drosophila homeodomain transcription factor Vnd associates with a variety of co-factors is extensively phosphorylated and forms multiple complexes in embryos Huanqing Zhang1 z Li-Jyun Syu1 f Vicky Modica1 Zhongxin Yu1 Tonia Von Ohlen2 and Dervla M. Mellerick1 1 MSRBIII Ann Arbor MI USA 2 Division of Biology Kansas State University Manhattan KS USA Keywords co-factor complex regulation transcription Vnd Correspondence D. M. Mellerick Med Sci I M5240 Ann Arbor MI 48109-0602 USA Fax 1 734 369 3874 Tel 1 734 709 3222 E-mail dervlamellerick@yahoo.com Present address 5051 BSRB Ann Arbor MI USA 1500 E. MedicalCenter Drive Ann Arbor MI USA Received 28 April2008 revised 23 July 2008 accepted 12 August 2008 doi 10.1111 j.1742-4658.2008.06639.x Vnd is a dual transcriptional regulator that is essential for Drosophila dorsal-ventral patterning. Yet our understanding of the biochemical basis for its regulatory activity is limited. Consistent with Vnd s ability to repress target expression in embryos endogenously expressed Vnd physically associates with the co-repressor Groucho in Drosophila Kc167 cells. Vnd exists as a single complex in Kc167 cells in contrast with embryonic Vnd which forms multiple high-molecular-weight complexes. Unlike its vertebrate homolog Nkx2.2 full-length Vnd can bind its target in electrophoretic mobility shift assay suggesting that co-factor availability may influence Vnd s weak regulatory activity in transient transfections. We identify the high mobility group 1-type protein D1 and the novel helix-loop-helix protein Olig as novel Vnd-interacting proteins using co-immunoprecipitation assays. Furthermore we demonstrate that both D1 and Olig are co-expressed with Vnd during Drosophila embryogenesis consistent with a biological basis for this interaction. We also suggest that the phosphorylation state of Vnd influences its ability to interact with co-factors because Vnd is extensively phosphorylated in embryos and can be phosphorylated .