DLP, a novel Dim1 family protein implicated in pre-mRNA splicing and cell cycle progression

In eukaryotes, primary transcripts undergo a splicing process that removes intronic sequences by a macromolecular enzyme known as the spliceosome. Both genetic and biochemical studies have revealed that essential components of the spliceosome include five small RNAs, U1, U2, U4, U5, and U6, and as many as 300 distinct proteins. Here we report the molecular cloning and functional analysis of a novel cDNA encoding for a protein of 149 amino acids. This protein has 38% amino acid sequence identity with and is evolutionally related to yeast Dim1 protein. Hence we named this protein DLP for Dim1-like protein. We showed that DLP is required for S/G₂ transition. We also demonstrated that DLP functions in cell nucleus and interacts with the U5-102-kBa protein subunit of the spliceosome, and blocking DLP protein activity led to an insufficient pre-mRNA splicing, suggesting that DLP is yet another protein component involved in pre-mRNA splicing. Collectively, our experiments indicated that DLP is implicated in not only cell cycle progression but also in a more specific molecular process such as pre-mRNA splicing.