Pre-mRNA Processing Factor 38A (PRPF38A)

PRP38 has been genetically identified in a screen of temperature-sensitive mutants of Saccharomyces cerevisiae. Shifting temperature-sensitive prp38 cultures from 23 to 37oC prevents the first cleavage-ligation event in the excision of introns from mRNA precursors. In vitro splicing inactivation and complementation studies suggest that the PRP38-encoded factor functions, at least in part, after stable splicing complex formation. The PRP38 locus contains a 726-bp open reading frame coding for an acidic 28-kDa polypeptide (PRP38). While PRP38 lacks obvious structural similarity to previously defined splicing factors, heat inactivation of PRP38, PRP19, or any of the known U6 small nuclear ribonucleoprotein-associating proteins leads to a common, unexpected consequence: intracellular U6 small nuclear RNA levels decrease as splicing activity is lost.