Mechanisms of genomic instability, tumor initiation and progression following the disruption of the RTF2-RNase H2 axis

Project Summary/Abstract
The aberrant incorporation or retention of ribonucleic acids (RNAs) in the genome is a common cause of genomic
instability, rendering it susceptible to hydrolysis and downstream mutagenesis. The enzyme RNase H2 is one of
the primary mechanisms protecting against this destabilization of the genome by removing these genome-
embedded RNAs.
Our lab recently uncovered a novel mechanism of regulation of RNase H2, by uncovering that replication
termination factor 2 (RTF2) is involved in localizing and regulating the levels of RNase H2 at the replication fork.
Further elucidation of this interaction is required to understand the basic biology behind the regulation and
function of how RNase H2 prevents genome instability. Interestingly, copy number loss of RNase H2 is commonly
found in Chronic Lymphocytic Leukemia (CLL), in over 30% of cases. In my preliminary work, I have developed
various cellular models in which RNase H2 and RTF2 can be depleted, and I have expressed and purified
recombinant RNase H2 and RTF2, allowing for both in vivo studies of which RNase H2 activities are regulated
by RTF2 and in vitro studies of their interaction. Furthermore, I have developed a novel assay allowing a
quantitative analysis of ribonucleotide incorporation in the genomes of human cells. This assay will be used to
study the regulation of RNase H2 by RTF2, and will be assessed in its applicability to predict CLL responses to
PARP-inhibitors. The direct mechanism behind tumor progression in the loss of RNase H2 has not been studied.
In this proposal, building on my above preliminary work, I will test the hypothesis that RTF2 interacts directly with
and regulates the activities of RNase H2 at the replication fork and examine the mechanism behind how loss of
RNase H2 compromises genomic stability and leads to tumor progression.
I am an MD/PhD student at the Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional Program, where I am
in the laboratory of Dr. Agata Smogorzewska at The Rockefeller University. My long-term goal is to become a
physician scientist, practicing as a hematologist-oncologist as well as running an independent basic science lab
as an academic university hospital. The plan outlined in this proposal, along with the support and mentorship of
Dr. Agata Smogorzewska, my thesis research committee, and the Tri-Institutional MD-PhD program will help me
achieve these career aspirations.

Grant Number: 5F30CA268717-04
NIH Institute/Center: NIH
Principal Investigator: Nicolas Blobel