RNA:DNA hybrids from Okazaki fragments contribute to establish the Ku-mediated barrier to replication-fork degradation.

Nonhomologous end-joining (NHEJ) factors act in replication-fork protection, restart, and repair. Here, we identified a mechanism related to RNA:DNA hybrids to establish the NHEJ factor Ku-mediated barrier to nascent strand degradation in fission yeast. RNase H activities promote nascent strand degradation and replication restart, with a prominent role of RNase H2 in processing RNA:DNA hybrids to overcome the Ku barrier to nascent strand degradation.

Nrd1p identifies aberrant and natural exosomal target messages during the nuclear mRNA surveillance in Saccharomyces cerevisiae.

Nuclear degradation of aberrant mRNAs in Saccharomyces cerevisiae is accomplished by the nuclear exosome and its cofactors TRAMP/CTEXT. Evidence from this investigation establishes a universal role of the Nrd1p-Nab3p-Sen1p (NNS) complex in the nuclear decay of all categories of aberrant mRNAs. In agreement with this, both nrd1-1 and nrd1-2 mutations impaired the decay of all classes of aberrant messages.

Localization elements and zip codes in the intracellular transport and localization of messenger RNAs in Saccharomyces cerevisiae.

Intracellular trafficking and localization of mRNAs provide a mechanism of regulation of expression of genes with excellent spatial control. mRNA localization followed by localized translation appears to be a mechanism of targeted protein sorting to a specific cell-compartment, which is linked to the establishment of cell polarity, cell asymmetry, embryonic axis determination, and neuronal plasticity in metazoans. However, the complexity of the mechanism and the components of mRNA localization in higher organisms prompted the use of the unicellular organism Saccharomyces cerevisiae as a simplified model organism to study this vital process.

DRN and TRAMP degrade specific and overlapping aberrant mRNAs formed at various stages of mRNP biogenesis in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, nuclear exosome along with TRAMP and DRN selectively eliminates diverse aberrant messages. These decay apparatuses appear to operate as independent mechanisms in the nucleus. Here, using genetic and molecular approach we systematically investigate the functional relationship between exosome, TRAMP and DRN mechanisms by examining their relative contributions in the degradation of diverse classes of aberrant nuclear mRNAs generated at various phases of mRNP biogenesis.