TUT7 catalyzes the uridylation of the 3' end for rapid degradation of histone mRNA.
The replication-dependent histone mRNAs end in a stem-loop instead of the poly(A) tail present at the 3' end of all other cellular mRNAs. Following processing, the 3' end of histone mRNAs is trimmed to 3 nucleotides (nt) after the stem-loop, and this length is maintained by addition of nontemplated uridines if the mRNA is further trimmed by 3'hExo. These mRNAs are tightly cell-cycle regulated, and a critical regulatory step is rapid degradation of the histone mRNAs when DNA replication is inhibited. An initial step in histone mRNA degradation is digestion 2-4 nt into the stem by 3'hExo and uridylation of this intermediate. The mRNA is then subsequently degraded by the exosome, with stalled intermediates being uridylated. The enzyme(s) responsible for oligouridylation of histone mRNAs have not been definitively identified. Using high-throughput sequencing of histone mRNAs and degradation intermediates, we find that knockdown of TUT7 reduces both the uridylation at the 3' end as well as uridylation of the major degradation intermediate in the stem. In contrast, knockdown of TUT4 did not alter the uridylation pattern at the 3' end and had a small effect on uridylation in the stem-loop during histone mRNA degradation. Knockdown of 3'hExo also altered the uridylation of histone mRNAs, suggesting that TUT7 and 3'hExo function together in trimming and uridylating histone mRNAs.
Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
Patrick E
PE
Lackey
Department of Computer Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
Joshua D
JD
Welch
Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.|Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
William F
WF
Marzluff
D002384:Catalysis; D004261:DNA Replication; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006657:Histones / Q000235:genetics*; D006801:Humans; D006868:Hydrolysis; D012316:RNA Nucleotidyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D014529:Uridine / Q000378:metabolism*
D006657:Histones; D012333:RNA, Messenger; D012316:RNA Nucleotidyltransferases; C576505:TUT7 protein, human; D014529:Uridine
histone mRNA; mRNA degradation; uridylation