A number of genes have been identified in the fully sequenced genome of Saccharomyces cerevisiae that appear to be conserved throughout evolution and the function of which remains poorly understood. In this manuscript we describe the initial characterization of yeast BUD31 gene. cDNA sequences highly related to BUD31 have been identified in human, Xenopus laevis, and Caenorhabditis elegans. With the aim of further understanding its function, we generated a BUD31-null yeast strain and characterized its phenotype: bud31 mutant cells showed severe cytoskeletal abnormalities, with dramatic effects on actin distribution and bud formation. We also proceeded to identify interacting proteins using the tandem affinity-purification method, coupled to mass spectrometry: Bud31p was found in complex with proteins involved in mRNA splicing. We propose that the observed phenotypes for bud31-null strain could be the result of defective splicing and indicate a first functional role for Bud31p and its homologs. (C) 2004 Elsevier Inc. All rights reserved.