Biochemical and Genetic Evidence Supports Fyv6 as a Second-Step Splicing Factor in Saccharomyces cerevisiae

Abstract

Precursor mRNA (pre-mRNA) splicing is an essential process for gene expression in 15 eukaryotes catalyzed by the spliceosome in two transesterification steps. The spliceosome is a 16 large, highly dynamic complex composed of 5 small nuclear RNAs and dozens of proteins, some 17 of which are needed throughout the splicing reaction while others only act during specific stages. 18 The human protein FAM192A was recently proposed to be a splicing factor that functions during 19 the second transesterification step, exon ligation, based on analysis of cryo-electron microscopy 20 (cryo-EM) density. It was also proposed that Fyv6 might be the functional S. cerevisiae homolog 21 of FAM192A; however, no biochemical or genetic data has been reported to support this 22 hypothesis.