# SLX4 in Nuclease Recruitment

> **NIH NIH SC1** · CALIFORNIA STATE UNIVERSITY NORTHRIDGE · 2020 · $350,008

## Abstract

PROJECT SUMMARY AND ABSTRACT
 Ionizing radiation and chemical agents induce strand breaks in DNA, which give rise to mutations and
chromosomal alterations that can cause cancer. One of the chief biological defenses against DNA strand
breaks is Double-Strand Break (DSB) repair, a complicated family of biologic pathways. Some modes of DSB
Repair can proceed with full restoration of the DNA sequence, but others result in significant sequence change
or loss. Many important questions remain regarding biochemical requirements for pathway selection.
 Within these broader issues are more specific questions regarding the mechanism of recruitment of
proteins that participate in some DSB repair pathways but not others. In baker's yeast (S. cerevisiae), Slx4
protein recruits any of several endonucleases to DSB sites, which either remove an extraneous
nonhomologous stretch of DNA or incise a four-way junction of DNA (a Holliday Junction) as one of the last
steps of the repair event. The endonucleases recruited by Slx4 include Rad1-Rad10, Mus81-Mms4 and Yen1,
but the biochemical details governing the selection of one endonuclease over another are not understood in
sufficient detail. It is becoming increasingly clear that the phase of the cell cycle plays a critical role in
endonuclease access and engagement of the DSB site. This project will detail the role of Slx4 in recruitment of
endonucleases to DSBs in the yeast S. cerevisiae, focusing on why the SLX4 gene is needed for recruitment
of endonuclease Rad1-Rad10 in some phases of the cell cycle but not others. The specific aims of this
proposal are to: 1) determine whether cells that are not actively engaged in cell division (those in G1) require
SLX4 for repair product formation, 2) investigate whether Rad1-Rad10 recruitment to several specific types of
DSB sites depends on SLX4 only in S phase, 3) investigate whether checkpoint signal dampening by Slx4
plays a role in SLX4-dependent recruitment of Rad1-Rad10 in DSB repair in dividing cells and, 4) determine
whether Rad1-Rad10 colocalizes with Mus81-Mms4 or Yen1 in last-minute DNA repair during the final
moments of chromosome separation in cell division and if such localization is SLX4-dependent.
 These aims will be investigated with a variety of experimental techniques, including a relatively novel
fluorescence microscopy approach in which DSBs will be induced and their repair monitored by fluorescence
imaging of convergent fluorescent signals. In vitro techniques such as quantitative PCR and Chromatin
Immunoprecipitation will also be used to provide corroborating results. These experiments will address
important questions regarding the genetic and biochemical requirements for recruitment of Rad1-Rad10,
Mus81-Mms4 and Yen1 to DSB sites. All three nucleases are conserved in all eukaryotes including humans.
Understanding the molecular basis for genome instability will inform our understanding of the causes of cancer
and aging, and will be important for advanc...

## Key facts

- **NIH application ID:** 9973223
- **Project number:** 5SC1GM127204-03
- **Recipient organization:** CALIFORNIA STATE UNIVERSITY NORTHRIDGE
- **Principal Investigator:** Paula Louise Fischhaber
- **Activity code:** SC1 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $350,008
- **Award type:** 5
- **Project period:** 2018-08-08 → 2022-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9973223

## Citation

> US National Institutes of Health, RePORTER application 9973223, SLX4 in Nuclease Recruitment (5SC1GM127204-03). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/9973223. Licensed CC0.

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