In eukaryotes, primary transcripts undergo a splicing process which 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 reported 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 evolutionary 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 KD 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.