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Alternative forms of Max as enhancers or suppressors of Myc-ras cotransformation
T P Mäkelä1, P J Koskinen, I Västrik
1Department of Virology, University of Helsinki, Finland.
Abstract:
Max is a basic-helix-loop-helix-leucine zipper protein capable of forming sequence-specific DNA binding complexes with Myc proteins. An alternatively spliced messenger RNA has been identified that encodes a form of Max truncated at the COOH-terminus. This delta Max protein retained the ability to bind to the CACGTG motif in a complex with c-Myc but lacks the nuclear localization signal and the putative regulatory domain of Max. When tested in a myc-ras cotransformation assay in rat embryo fibroblasts, Max suppressed, whereas delta Max enhanced, transformation. Thus, the max gene may encode both a negative and a positive regulator of c-Myc function.
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