TY - JOUR
T1 - Studies with recombinant U7 snRNP demonstrate that CPSF73 is both an endonuclease and a 5′-3′ exonuclease
AU - Yang, Xiao Cui
AU - Yadong, S. U.N.
AU - AIK, Wei Shen
AU - Marzluff, William F.
AU - Tong, Liang
AU - Dominski, Zbigniew
N1 - Funding Information:
This research was funded by the National Institutes of Health (NIH) grants R01GM029832 to Z.D. and W.F.M., and R35GM118093 to L.T. W.S.A. was supported by a fellowship from the Raymond and Beverley Sackler Center for Research at Convergence of Disciplines at Columbia University Medical Center.
PY - 2020/10
Y1 - 2020/10
N2 - Metazoan replication-dependent histone pre-mRNAs are cleaved at the 3′′ end by U7 snRNP, an RNA-guided endonuclease that contains U7 snRNA, seven proteins of the Sm ring, FLASH, and four polyadenylation factors: symplekin, CPSF73, CPSF100, and CstF64. A fully recombinant U7 snRNP was recently reconstituted from all 13 components for functional and structural studies and shown to accurately cleave histone pre-mRNAs. Here, we analyzed the activity of recombinant U7 snRNP in more detail. We demonstrate that in addition to cleaving histone pre-mRNAs endonucleolytically, reconstituted U7 snRNP acts as a 5′′-3′′ exonuclease that degrades the downstream product generated from histone pre-mRNAs as a result of the endonucleolytic cleavage. Surprisingly, recombinant U7 snRNP also acts as an endonuclease on single-stranded DNA substrates. All these activities depend on the ability of U7 snRNA to base-pair with the substrate and on the presence of the amino-terminal domain (NTD) of symplekin in either cis or trans, and are abolished by mutations within the catalytic center of CPSF73, or by binding of the NTD to the SSU72 phosphatase of RNA polymerase II. Altogether, our results demonstrate that recombinant U7 snRNP functionally mimics its endogenous counterpart and provide evidence that CPSF73 is both an endonuclease and a 5′′-3′′ exonuclease, consistent with the activity of other members of the β-CASP family. Our results also raise the intriguing possibility that CPSF73 may be involved in some aspects of DNA metabolism in vivo.
AB - Metazoan replication-dependent histone pre-mRNAs are cleaved at the 3′′ end by U7 snRNP, an RNA-guided endonuclease that contains U7 snRNA, seven proteins of the Sm ring, FLASH, and four polyadenylation factors: symplekin, CPSF73, CPSF100, and CstF64. A fully recombinant U7 snRNP was recently reconstituted from all 13 components for functional and structural studies and shown to accurately cleave histone pre-mRNAs. Here, we analyzed the activity of recombinant U7 snRNP in more detail. We demonstrate that in addition to cleaving histone pre-mRNAs endonucleolytically, reconstituted U7 snRNP acts as a 5′′-3′′ exonuclease that degrades the downstream product generated from histone pre-mRNAs as a result of the endonucleolytic cleavage. Surprisingly, recombinant U7 snRNP also acts as an endonuclease on single-stranded DNA substrates. All these activities depend on the ability of U7 snRNA to base-pair with the substrate and on the presence of the amino-terminal domain (NTD) of symplekin in either cis or trans, and are abolished by mutations within the catalytic center of CPSF73, or by binding of the NTD to the SSU72 phosphatase of RNA polymerase II. Altogether, our results demonstrate that recombinant U7 snRNP functionally mimics its endogenous counterpart and provide evidence that CPSF73 is both an endonuclease and a 5′′-3′′ exonuclease, consistent with the activity of other members of the β-CASP family. Our results also raise the intriguing possibility that CPSF73 may be involved in some aspects of DNA metabolism in vivo.
KW - 3 end processing
KW - CPSF73
KW - Histone pre-mRNA
KW - Symplekin
KW - U7 snRNP
UR - http://www.scopus.com/inward/record.url?scp=85091129727&partnerID=8YFLogxK
U2 - 10.1261/rna.076273.120
DO - 10.1261/rna.076273.120
M3 - Journal article
C2 - 32554553
AN - SCOPUS:85091129727
SN - 1355-8382
VL - 26
SP - 1345
EP - 1359
JO - RNA
JF - RNA
IS - 10
ER -