# Mechanisms of Developmental Regulation in Chlamydia

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA-IRVINE · 2020 · $457,671

## Abstract

Project Summary/Abstract
Chlamydia is one of the most important infectious agents from a public health
perspective. More than 1.5 million cases of chlamydial infections are reported to the
CDC annually, making it the most commonly reported infectious disease in the U.S.
Chlamydia causes an unusual intracellular infection in which there is conversion
between two developmental forms of the bacterium: the elementary body (EB), which is
the infectious but dormant form, and the reticulate body (RB), which is the intracellular,
replicating form. Gene expression is limited to RBs, and transcriptional silencing in EBs
has been attributed to DNA condensation by two histone-like proteins, HctA and HctB.
We hypothesize a second silencing mechanism in which RNA polymerase in EBs is
inhibited in a reversible manner that is controlled by Type 3 secretion (T3S) activity. In
Aim 1 we will study how a T3S chaperone Scc4, together with two other T3S proteins,
coordinately regulates RNA polymerase activity and T3S secretion activity. In Aim 2, we
will investigate a second T3S chaperone Scc2 that we propose as a T3S-regulated
silencer of chlamydial transcription. In Aim 3, we will study the histone-like proteins to
determine if they silence transcription uniformly or in a promoter-specific manner. These
studies will define the mechanisms of transcriptional silencing in EBs, which is a central
feature of developmental gene regulation in the intracellular Chlamydia infection and a
potential therapeutic target.

## Key facts

- **NIH application ID:** 9913440
- **Project number:** 5R01AI044198-19
- **Recipient organization:** UNIVERSITY OF CALIFORNIA-IRVINE
- **Principal Investigator:** Ming Tan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $457,671
- **Award type:** 5
- **Project period:** 1999-08-01 → 2022-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9913440

## Citation

> US National Institutes of Health, RePORTER application 9913440, Mechanisms of Developmental Regulation in Chlamydia (5R01AI044198-19). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9913440. Licensed CC0.

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