MAID - A MATERNALLY TRANSCRIBED NOVEL GENE ENCODING A POTENTIAL NEGATIVE REGULATOR OF BHLH PROTEINS IN THE MOUSE EGG AND ZYGOTE

We isolated an abundant novel cDNA SSEC-8 from a subtraction cDNA libr ary enriched for maternal transcripts that are still present in the mo use 2 cell stage embryo, This gene is evolutionarily conserved and map s to the distal region of mouse chromosome 2. The deduced polypeptide sequence of the encoded protein contains a conserved helix-loop-helix (HLH) motif without a basic DNA binding domain, suggesting that it fun ctions as a negative regulator of basic (b) HLH transcription factors. Gel mobility shift assays show that in vitro translated protein preve nts the E12/MyoD bHLH dimer from binding to DNA, Also, transient overe xpression of this protein in C2C12 cells reduced the transcription of a CAT-reporter regulated by an E12/MyoD driven enhancer, The 3'-UTR co ntains consensus sequences of cytoplasmic polyadenylation elements (CP E's), and the length of its poly (A) tail changes during oocyte matura tion, indicating that its expression is controlled by timely activatio n of translation, This new gene, Maid, models the translational and tr anscriptional regulation of gene expression during the transition from gamete to embryo. (C) 1997 Wiley-Liss, Inc.