# IONIZING RADIATION MUTAGENESIS IN ESCHERICHIA COLI

> **NIH NIH R01** · STANFORD UNIVERSITY · 1989 · $176,231

## Abstract

One important finding from our studies on ionizing radiation
mutagenesis (IRM).  In Escherichia coli is that IRM is not
uniformly dependent on the umuDC genes as is the case for UV
radiation mutagenesis.  That is, there are umuDC-dependent and
umuDC-independent mechanisms of IRM.  We have already
isolated and begun mapping xmu (X-ray mutability) mutations that
block umuDC-independent IRM, and that appear to be distinct
from the recA, lexA, and umuDC loci.  Towards our long-term
objective of understanding the molecular basis of IRM, we propose
to accomplish the following specific aims:  (1) to determine the
number and exact location of the xmu genes using the genetic
procedures of conjugation and transduction (presently there
appear to be three loci); (2) to clone at least two xmu genes
(during this grant period) into useful plasmids in order to identify
and characterize their gene products using the maxicell technique
and SDS-polyacrylamide gel electrophoresis; (3) to fuse the
plasmid-carried xmu genes with a lacZ gene in order to study the
regulation of xmu genes using an assay for beta-galactosidase; (4)
to use the well-characterized his trp reversion system to
determine the mutational spectra in the xmu strains under several
irradiation conditions, and for chemical mutagens that produce
specific types of DNA damage; (5) to test whether the xmu
mutations inhibit induction of the recA gene, using a recA::lacZ
fusion and an assay for beta galactosidase activity, and to test
whether xmu mutations can be suppressed by mutations in other
genes, and to test whether xmu mutations confer radiation
sensitivity; (6) to determine the nucleotide sequences of xmu
genes using the dideoxy-chain termination method of Sanger in
order to formulate models for xmu gene action.

Health Relatedness:  This proposal suggests genetic and molecular
biological procedures for increasing the understanding of the
molecular mechanisms of IRM.  Since mutagenesis and
carcinogenesis are known to be linked, this research should
provide valuable insights into the molecular mechanism of
ionizing radiation carcinogenesis.

## Key facts

- **NIH application ID:** 3171518
- **Project number:** 5R01CA033738-07
- **Recipient organization:** STANFORD UNIVERSITY
- **SAM.gov UEI:** HJD6G4D6TJY5
- **Principal Investigator:** KENDRIC C SMITH
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1989
- **Award amount:** $176,231
- **Award type:** 5
- **Project period:** 1983-02-01 → 1991-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3171518

## Citation

> US National Institutes of Health, RePORTER application 3171518, IONIZING RADIATION MUTAGENESIS IN ESCHERICHIA COLI (5R01CA033738-07). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3171518. Licensed CC0.

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