Involvement of Telomerase Reverse Transcriptase in Heterochromatin Maintenance

Abstract

In the fission yeast Schizosaccharomyces pombe, centromeric heterochromatin is maintained by an RNA-directed RNA polymerase complex (RDRC) and the RNA-induced transcriptional silencing (RITS) complex in a manner that depends on the generation of short interfering RNA. In association with the telomerase RNA component (TERC), the telomerase reverse transcriptase (TERT) forms telomerase and counteracts telomere attrition, and without TERC, TERT has been implicated in the regulation of heterochromatin at locations distinct from telomeres. Here, we describe a complex composed of human TERT (hTERT), Brahma-related gene 1 (BRG1), and nucleostemin (NS) that contributes to heterochromatin maintenance at centromeres and transposons. This complex produced double-stranded RNAs homologous to centromeric alpha-satellite (alphoid) repeat elements and transposons that were processed into small interfering RNAs targeted to these heterochromatic regions. These small interfering RNAs promoted heterochromatin assembly and mitotic progression in a manner dependent on the RNA interference machinery. These observations implicate the hTERT/BRG1/NS (TBN) complex in heterochromatin assembly at particular sites in the mammalian genome.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00093-14.

ACKNOWLEDGMENTS

We thank Fuyuki Ishikawa for the gift of mTERT-knockout mice and Satomi Kuramochi-Miyagawa, Tokio Tani, and Hiroyuki Seimiya for providing technical assistance with RT-PCR analysis of LINE elements, satellite I RT-PCR, and TRAP assays, respectively. We thank Medical and Biological Laboratories Co., Ltd., for their assistance in creating the hTERT MAb.

This work was supported in part by a Grant-in-Aid for Young Scientists (B) (S.O.), a funding program for the Next Generation World-Leading Researchers (NEXT program) (K.M.), the Takeda Science Foundation (K.M.), the Kato Memorials Bioscience Foundation (K.M.), and National Cancer Center Research and Development Funds (23-A-8 to T.S., 23-A-7 to K.K., and 23-B-5 to K.M.). N.O. was a Research Fellow of the Japan Society for the Promotion of Science.

N.O., M.Y., S.O., K.K., Y.M., S.Y., T.K.I., T.M., and H.N. performed experiments. Y.T. and T.S. designed and carried out the bioinformatics analyses. M.Y., Y.M., and K.M. designed the experiments and discussed the interpretation of the results. K.M. and Y.M. wrote the manuscript.