# MURINE CORONAVIRUS RNA SYNTHESIS

> **NIH NIH R01** · UNIVERSITY OF SOUTHERN CALIFORNIA · 1992 · $211,957

## Abstract

The overall objective of this grant application is to understand the
mechanism of RNA synthesis of mouse hepatitis virus (MHV), a murine
coronavirus.  During the last grant period, our laboratory has established
two unique mechanisms associated with MHV RNA synthesis, leader-primed
transcription of subgenomic   mRNAs and high-frequency RNA recombination.
These phenomena suggest that MHV RNA synthesis is discontinuous and
nonprocessive.  We have also started to characterized the structure and
properties of the virus-specific RNA polymerases, and have found an
autoproteolytic activity associated with the precursor of the RNA
polymerase.  These data, along with an unusually large size of the
possible RNA polymerase gene (more than 23 kb) and the large size of MHV
RNA genome (32 kb), indicate that MHV RNA synthesis is extremely complex.

This grant application proposes to continue our studies on the mechanism
of MHV RNA synthesis.  Four projects will be carried out: (1)
Identification of natural transcriptional initiation sites on MHV genome.
We will characterize the transcriptional initiation sequences of the minor
mRNAs and "anomalous" mRNA species which are expressed only in some MHV
strains.  Both leader RNAs and template sequences at the transcriptional
initiation sites will be studies; (2) Development and characterization of
an in vitro transcription system for MHV.  We will use a lysolecithin
permeabilization method to establish an in vitro system to study the
detailed mechanism of leader-primed transcription and the sequence
requirement for both the leader RNA and transcriptional initiation sites;
(3) Characterization of the polyprotein encoded by gene 1 of MHV.  This
protein probably is the precursor to the virus-specific RNA polymerases.
We will study its gene sequence and protein processing.  We will also
attempt to      identify the enzymatic activities, including proteases and
helicase activities associated with these proteins.  Finally, we will
study whether these proteins can complement temperature-sensitive mutants
which are defective in RNA synthesis; and (4) Characterization of
transcriptional and post-transcriptional regulation of gene 2b expression.
We will particularly study the mechanism by which A59 strain synthesizes
gp65 despite the fact that the virus does not have a complete open reading
frame for this protein.

These projects are expected to shed further light on the mechanism of RNA
synthesis and gene regulation in MHV.

## Key facts

- **NIH application ID:** 3128591
- **Project number:** 5R01AI019244-11
- **Recipient organization:** UNIVERSITY OF SOUTHERN CALIFORNIA
- **SAM.gov UEI:** G88KLJR3KYT5
- **Principal Investigator:** Michael M.C. Lai
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1992
- **Award amount:** $211,957
- **Award type:** 5
- **Project period:** 1982-08-01 → 1995-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3128591

## Citation

> US National Institutes of Health, RePORTER application 3128591, MURINE CORONAVIRUS RNA SYNTHESIS (5R01AI019244-11). Retrieved via MORVS 2026-10-24 from https://api.morvs.ai/grant/nih/3128591. Licensed CC0.

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