Poster abstracts
Poster number 108 submitted by Jie Qu
A transcription factor aids in noncoding RNA-templated replication by DNA-dependent RNA polymerase II
Jie Qu (Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA), Ying Wang and Jian Wu (Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA), Shaoyi ji and Yi Li (College of Life Sciences, Peking University, Beijing, China), Andrew Wallace, Venkat Gopalan (Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA), David M. Bisaro (Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA), Biao Ding (Deceased, Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA)
Abstract:
Some DNA-dependent RNA polymerases (DdRP) possess RNA-dependent RNA polymerase activity, suggesting their evolution from RdRPs that first arose to transcribe RNA templates. This relic RdRP activity is required for transcription of certain noncoding RNAs that regulate gene expression, and for replication of plant viroids and human hepatitis delta virus. Here, we used Potato spindle tuber viroid (PSTVd) as a model to uncover cellular factor(s) that regulate RNA-templated replication. RNA polymerase II (Pol II)-catalyzed replication of PSTVd in the nucleoplasm employs a rolling-circle mechanism that involves the generation of (+)- and (-)-strand RNAs. We report here that the 7-zinc finger (ZF) transcription factor IIIA (NbTFIIIA-7ZF) from Nicotiana benthamiana, a shorter variant of the DNA template-specific 9-ZF TFIIIA (NbTFIIIA-9ZF), interacts with Pol II in vivo and is essential for PSTVd replication. Both forms of NbTFIIIA interact with the (+)-strand, but only NbTFIIIA-7ZF interacts with PSTVd (-)-strand in vitro and in vivo. Antisense-mediated suppression of NbTFIIIA decreased PSTVd replication, but only overexpression of NbTFIIIA-7ZF, and not NbTFIIIA-9ZF, enhanced replication. Consistent with known sites of PSTVd replication, NbTFIIIA-7ZF localizes to the nucleoplasm and the nucleolus, whereas NbTFIIIA-9ZF is confined to the nucleolus. Further, footprinting assays revealed that NbTFIIIA-7ZF binds to a region of PSTVd critical for initiating PSTVd transcription. Our results identify NbTFIIIA-7ZF as a dedicated cellular transcription factor in DdRP-catalyzed RNA-templated replication, highlighting both the extraordinary evolutionary adaptation of viroids and the potential of DdRPs for a broad role in cellular processes.
This work was supported by NSF grant IOS-1354636 to B. D. and D. M. B.
This abstract is dedicated to the memory of Dr. Biao Ding
Keywords: Viroid, Transcription factor, noncoding RNA