Importance of polyadenylation in the selective elimination of meiotic mRNAs in growing S. pombe cells

Abstract

A number of meiosis-specific mRNAs are initially weakly transcribed, but then selectively removed during fission yeast mitotic growth. These mRNAs harbour a region termed DSR (determinant of selective removal), which is recognized by the YTH family RNA-binding protein Mmi1p. Mmi1p directs the destruction of these mRNAs in collaboration with nuclear exosomes. However, detailed molecular mechanisms underlying this process of selective mRNA elimination have remained elusive. In this study, we demonstrate the critical role of polyadenylation in this process. Two-hybrid and genetic screens revealed potential interactions between Mmi1p and proteins involved in polyadenylation. Additional investigations showed that destruction of DSR-containing mRNAs by exosomes required polyadenylation by a canonical poly(A) polymerase. The recruitment of Pab2p, a poly(A)-binding protein, to the poly(A) tail was also necessary for mRNA destruction. In cells undergoing vegetative growth, Mmi1p localized with exosomes, Pab2p, and components of the polyadenylation complex in several patchy structures in the nucleoplasm. These patches may represent the sites for degradation of meiosis-specific mRNAs with untimely expression.

Conserved factor Dhp1/Rat1/Xrn2 triggers premature transcription termination and nucleates heterochromatin to promote gene silencing

“…Given the functional connection between 3′-end processing and degradation factors (18)(19)(20)(21), we asked whether the elimination factors Mmi1 and Rrp6 are required for premature termination of DSR-containing gene transcripts. Remarkably, the loss of Mmi1 or Rrp6 prevented premature termination of ssm4 and mcp5 transcripts upstream of the DSR (Fig.…”

Execution of the meiotic noncoding RNA expression program and the onset of gametogenesis in yeast require the conserved exosome subunit Rrp6

“…Moreover, the exosome, which includes the RNase D-type exoribonuclease Rrp6 involved in mitotic ncRNA turnover, is conserved from yeasts to mammals (8)(9)(10)(11). Importantly, the fission yeast ortholog of Rrp6 was shown to be involved not only in the mitotic degradation of meiotic mRNAs but also of at least one meiotic noncoding transcript encoded by sme2 (12,13).…”

The Prp4 Kinase: Its Substrates, Function and Regulation in Pre-mRNA Splicing

“…However, distinct pathways of poly(A)-dependent mRNA degradation involving the nuclear poly(A)-binding protein (Pab2) and Rrp6 have been described in fission yeast [67][68][69][70][71]. Eukaryotic cells have developed several RNA surveillance pathways to prevent the expression of aberrant transcripts [72][73][74].…”