Prp2p, Prp16p, Prp22p, and Prp43p are members of
the DEAH-box family of ATP-dependent putative RNA helicases
required for pre-mRNA splicing in Saccharomyces cerevisiae.
Recently, mammalian homologues of Prp43p and Prp22p have
been described, supporting the idea that splicing in yeast
and man is phylogenetically conserved. In this study, we
show that a murine cell line resistant to the novel immunoregulatory
drug Leflunomide (AravaTM) overexpresses a 135-kDa
protein that is a putative DEAH-box RNA helicase. We have
cloned the human counterpart of this protein and show that
it shares pronounced sequence homology with Prp16p. Apart
from its N-terminal domain, which is rich in RS, RD, and
RE dipeptides, this human homologue of Prp16p (designated
hPrp16p) is 41% identical to Prp16p. Significantly, homology
is not only observed within the phylogenetically conserved
helicase domain, but also in Prp16p-specific sequences.
Immunofluorescence microscopy studies demonstrated that
hPrp16p co-localizes with snRNPs in subnuclear structures
referred to as speckles. Antibodies specific for hPrp16p
inhibited pre-mRNA splicing in vitro prior to the second
step. Thus, like its yeast counterpart, hPrp16p also appears
to be required for the second catalytic step of splicing.
Taken together, our data indicate that the human 135-kDa
protein identified here is the structural and functional
homologue of the yeast putative RNA helicase, Prp16p.