Differential Expression of the TFIIIB
Subunits Brf1 and Brf2 in Cancer Cells
Stephanie Cabarcas, Joby Jacob, and Ingrid
Veras, St. John’s University Students
Laura Schramm, Department of
Biological Sciences, St. John’s College of Liberal Arts and
Sciences
Abstract: RNA polymerase (pol) III
transcription is specifically elevated in a variety of cancers and
is a target of regulation by a variety of tumor suppressors and
oncogenes. Accurate initiation by RNA pol III is
dependent on TFIIIB. In higher eukaryotes, two forms of
TFIIIB have been characterized. TFIIIB required for proper
initiation from gene internal RNA pol III promoters is comprised of
TBP, Bdp1, and Brf1. Proper initiation from gene external RNA
pol III promoters requires TBP, Bdp1, and Brf2. We
hypothesized that deregulation of RNA polymerase III transcription
in cancer may be a consequence of altered TFIIIB expression Here,
we report: (1) the TFIIIB subunits Brf1 and Brf2 are differentially
expressed in a variety of cancer cell lines: (2) the Brf1 and Brf2
promoters differ in activity in cancer cell lines, and (3) VAI
transcription is universally elevated, as compared to U6, in
breast, prostate and cervical cancer cells. We conclude that
post-transcriptional regulation of the TFIIIB subunits Brf1 and
Brf2 may be key molecular events dictating RNA pol III
transcription rates in a breast, cervical and prostate cancer cell
lines.