The polyadenylation factor CPSF-73 is involved in histone-pre-mRNA processing.
During 3' end processing, histone pre-mRNAs are cleaved 5 nucleotides after a conserved stem loop by an endonuclease dependent on the U7 small nuclear ribonucleoprotein (snRNP). The upstream cleavage product corresponds to the mature histone mRNA, while the downstream product is degraded by a 5'-3' exonuclease, also dependent on the U7 snRNP. To identify the two nuclease activities, we carried out UV-crosslinking studies using both the complete RNA substrate and the downstream cleavage product, each containing a single radioactive phosphate and a phosphorothioate modification at the cleavage site. We detected a protein migrating at 85 kDa that crosslinked to each substrate in a U7-dependent manner. Immunoprecipitation experiments identified this protein as CPSF-73, a known component of the cleavage/polyadenylation machinery. These studies suggest that CPSF-73 is both the endonuclease and 5'-3' exonuclease in histone-pre-mRNA processing and reveal an evolutionary link between 3' end formation of histone mRNAs and polyadenylated mRNAs.
Dominski
Zbigniew
Z
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA. dominski@med.unc.edu
Yang
Xiao-cui
XC
Marzluff
William F
WF
D000818:Animals; D039223:Cleavage And Polyadenylation Specificity Factor / Q000235:genetics / Q000378:metabolism*; D004720:Endonucleases / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D005092:Exonucleases / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D026721:RNA 3' End Processing / Q000235:genetics*; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D020885:Ribonucleoprotein, U7 Small Nuclear / Q000235:genetics / Q000378:metabolism
D039223:Cleavage And Polyadenylation Specificity Factor; D006657:Histones; D012322:RNA Precursors; D012333:RNA, Messenger; D020885:Ribonucleoprotein, U7 Small Nuclear; D004720:Endonucleases; D005092:Exonucleases