The Nuclear Cap-Binding Complex Mediates Meiotic Silencing by Unpaired DNA.
In the filamentous fungusNeurospora crassa, cross walls between individual cells are normally incomplete, making the entire fungal network vulnerable to attack by viruses and selfish DNAs. Accordingly, several genome surveillance mechanisms are maintained to help the fungus combat these repetitive elements. One of these defense mechanisms is called meiotic silencing by unpaired DNA (MSUD), which identifies and silences unpaired genes during meiosis. Utilizing common RNA interference (RNAi) proteins, such as Dicer and Argonaute, MSUD targets mRNAs homologous to the unpaired sequence to achieve silencing. In this study, we have identified an additional silencing component, namely the cap-binding complex (CBC). Made up of cap-binding proteins CBP20 and CBP80, CBC associates with the 5' cap of mRNA transcripts in eukaryotes. The loss of CBC leads to a deficiency in MSUD activity, suggesting its role in mediating silencing. As confirmed in this study, CBC is predominantly nuclear, although it is known to travel in and out of the nucleus to facilitate RNA transport. As seen in animals but not in plants, CBP20's robust nuclear import depends on CBP80 inNeurosporaCBC interacts with a component (Argonaute) of the perinuclear meiotic silencing complex (MSC), directly linking the two cellular factors.
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
Logan M
LM
Decker
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
Hua
H
Xiao
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
Erin C
EC
Boone
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
Michael M
MM
Vierling
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
Benjamin S
BS
Shanker
Department of Biology, Barry University, Miami Shores, Florida 33161.
Shanika L
SL
Kingston
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
Shannon F
SF
Boone
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
Jackson B
JB
Haynes
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211 shiup@missouri.edu.
Patrick K T
PK
Shiu
D002467:Cell Nucleus / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D005800:Genes, Fungal; D008540:Meiosis; D009491:Neurospora / Q000166:cytology* / Q000235:genetics*; D039502:Nuclear Cap-Binding Protein Complex / Q000378:metabolism*; D011485:Protein Binding
D004271:DNA, Fungal; D039502:Nuclear Cap-Binding Protein Complex
Neurospora crassa; RNA interference (RNAi); cap-binding proteins (CBPs); meiosis; meiotic silencing by unpaired DNA (MSUD)