A CPSF-73 homologue is required for cell cycle progression but not cell growth and interacts with a protein having features of CPSF-100.
Formation of the mature 3' ends of the vast majority of cellular mRNAs occurs through cleavage and polyadenylation and requires a cleavage and polyadenylation specificity factor (CPSF) containing, among other proteins, CPSF-73 and CPSF-100. These two proteins belong to a superfamily of zinc-dependent beta-lactamase fold proteins with catalytic specificity for a wide range of substrates including nucleic acids. CPSF-73 contains a zinc-binding histidine motif involved in catalysis in other members of the beta-lactamase superfamily, whereas CPSF-100 has substitutions within the histidine motif and thus is unlikely to be catalytically active. Here we describe two previously unknown human proteins, designated RC-68 and RC-74, which are related to CPSF-73 and CPSF-100 and which form a complex in HeLa and mouse cells. RC-68 contains the intact histidine motif, and hence it might be a functional counterpart of CPSF-73, whereas RC-74 lacks this motif, thus resembling CPSF-100. In HeLa cells RC-68 is present in both the cytoplasm and the nucleus whereas RC-74 is exclusively nuclear. RC-74 does not interact with CPSF-73, and neither RC-68 nor RC-74 is found in a complex with CPSF-160, indicating that these two proteins form a separate entity independent of the CPSF complex and are likely involved in a pre-mRNA processing event other than cleavage and polyadenylation of the vast majority of cellular pre-mRNAs. RNA interference-mediated depletion of RC-68 arrests HeLa cells early in G(1) phase, but surprisingly the arrested cells continue growing and reach the size typical of G(2) cells. RC-68 is highly conserved from plants to humans and may function in conjunction with RC-74 in the 3' end processing of a distinct subset of cellular pre-mRNAs encoding proteins required for G(1) progression and entry into S phase.
Dominski
Zbigniew
Z
Program in Molecular Biology and Biotechnology, CB #3280, University of North Carolina, Chapel Hill, NC 27599. dominski@med.unc.edu.
Yang
Xiao-Cui
XC
Purdy
Matthew
M
Wagner
Eric J
EJ
Marzluff
William F
WF
D000595:Amino Acid Sequence; D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D049108:Cell Enlargement; D002467:Cell Nucleus / Q000378:metabolism; D039223:Cleavage And Polyadenylation Specificity Factor / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D006367:HeLa Cells; D006639:Histidine / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011506:Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques
D039223:Cleavage And Polyadenylation Specificity Factor; D011506:Proteins; D034741:RNA, Small Interfering; D006639:Histidine