アクティブボード・２００８年１１月
　　　　　・・・・・２００８年１１月　４日更新・・・・・

研究発表を行った学会；
・第60回　日本細胞生物学会大会.
　２００８年６月２９日～７月１日(横浜)

タイトル；Screening for natural compounds that affect formation of nuclear speckles.
　
発表者；　志柿　花矢　氏
　　　（熊本大学　大学院自然科学研究科 理学専攻 谷研究室）
Abstract；
　Nuclear speckles are subnuclear structures that contain a number of splicing factors and factors involved in gene expression. Much debate has centered on the function and composition of these domains, either as sites for pre-mRNA metabolism including nuclear export or as storage sites of splicing factors. Speckles were shown to change their forms dynamically in response to state of gene expression. However, little is known about mechanisms of their formation and maintenance. To examine those mechanisms, we have screened 2016 actinomycetal culture supernatants for compounds that affect formation of nuclear speckles. For the screening, we immunostained splicing factor SF2/ASF, which is enriched in the speckles, after treatment with each culture supernatant and observed its cellular localization. As a result, we identified 15 positive samples that cause aberrant distributions of SF2. Of those, 1871-62a supernatant sample caused enlarged and rounded speckles. 1871-62a also induced changes in alternative splicing of the Clk1/Sty (splicing factor kinase) gene. Treatment with 1871-62a suppressed skipping of exon2 in Clk1/Sty alternative pre-mRNA splicing. Thus, 1871-62a seems to affect both formation of nuclear speckles and alternative splicing of pre-mRNA. Fractionation of the 1871-62a samples on HPLC and analysis of active fractions revealed that compounds causing observed phenotypes are staurosporine, which is an inhibitor for protein kinase C, and its derivative. It is, thus, suggested that inhibition of SF2 phosphorylation results in aberrant formation of nuclear speckles and suppression of exon-skipping in Clk/Sty alternative splicing. Purifications and characterizations of compounds in other positive supernatants are now in progress.