International Mammalian Genome Society

The 14th International Mouse Genome Conference (2000)

I32. Mouse Polycomb Proteins Mel18 and Ring1B Interact with the Spliceosome Protein SAP155

Kyoichi Isono1, Takeshi Akasaka1, Tomomi Kaneko1, Tsukasa Oda2, Masa-aki Muramatsu2, and Haruhiko Koseki1.
Dept. of Mol. Embryol., Grad. Sch. of Med., Chiba Univ., Japan,
Helix Res. Inst., Japan

Polycomb-group (PcG) proteins have originally been identified in Drosophila as repressors of expression of homeotic genes. PcG proteins form large, chromatin-associated multimeric complexes that are responsible for the stable transmission of gene activity through cell division. Although PcG homologs are found in other vertebrates such as human, mouse, chicken and Xenopus and evidence is also accumulating that PcG complexes have a variety of compositions, little is known about components of the PcG complexes and molecular mechanism of gene silencing by the complexes. In yeast two-hybrid screening with mouse PcG proteins as bait, we have identified the mouse SAP155 homolog as interaction protein with both Mel18 and Ring1B. SAP155 is characterized as an essential component of U2 snRNP for mRNA splicing in human and Xenopus in vitro. In GST pull-down assay we show that GST Mel18 and GST-Ring1B fusion proteins co-precipitate with the SAP155 homolog from cell nuclear extracts. To investigate genetic interactions between these PcG proteins and SAP155, we have made SAP155 gene deficient heterozygote (+/-) mice by gene targeting. No homozygote (-/-), however, is born because the fertilized eggs (-/-) cannot cleavage at very early stage during preimplantation, suggesting that SAP155 is essential in vivo. Molecular analyses in SAP155 (+/-) mice would be presented in this meeting.

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