Related Experiment Video

Updated: Aug 18, 2026

Chromatin Immunoprecipitation (ChIP) to Assay Dynamic Histone Modification in Activated Gene Expression in Human Cells
13:20

Chromatin Immunoprecipitation (ChIP) to Assay Dynamic Histone Modification in Activated Gene Expression in Human Cells

Published on: July 29, 2010

Transcriptional inhibition by Stat5. Differential activities at growth-related versus differentiation-specific

G Luo1, L Yu-Lee

  • 1Department of Microbiology and Immunology, Baylor College of Medicine, Houston, Texas 77030, USA.

The Journal of Biological Chemistry
|October 27, 1997
PubMed

Insights

Signal transducer and activator of transcription (Stat) proteins regulate gene expression. Stat5a and Stat5b can inhibit interferon regulatory factor-1 (IRF-1) gene induction while stimulating beta-casein, revealing a dual regulatory role.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Gene Regulation

Background:

  • Prolactin (PRL) signaling involves Janus kinases and signal transducer and activator of transcription (Stat) factors.
  • Stats play a crucial role in mediating PRL's effects on gene expression, including growth-related and differentiation-specific genes.

Purpose of the Study:

  • To investigate the specific roles of Stat5a and Stat5b in prolactin signaling.
  • To elucidate the mechanisms by which Stat5 proteins regulate the transcription of target genes like IRF-1 and beta-casein.

Main Methods:

  • Cloning of rat Stat5b from a PRL-responsive T cell line (Nb2).
  • Generation of a Stat5b-specific peptide antibody.
  • Transfection studies in PRL receptor-reconstituted COS cells with Stat5a or Stat5b.
  • Analysis of gene promoter activity using reporter assays.
  • Mutational analysis of Stat5b domains (DNA binding, transactivation).

Main Results:

  • Both Stat5a and Stat5b are tyrosine phosphorylated and bind to the IRF-1 GAS element in a PRL-inducible manner.
  • Unexpectedly, Stat5a and Stat5b inhibit PRL-induced IRF-1 promoter activity but stimulate beta-casein promoter activity.
  • Stat5-mediated inhibition of IRF-1 occurs at the native promoter, not a minimal GAS element, and requires the transactivation domain, suggesting protein-protein interactions.
  • Stat5b's DNA binding and transactivation domains are both necessary for beta-casein promoter stimulation.
  • A dominant-negative Stat5b mutant reverses Stat5b-mediated inhibition of the IRF-1 promoter.

Conclusions:

  • Stat proteins can function as both positive and negative regulators of gene transcription.
  • Stat5 can modulate gene expression through protein-protein interactions, independent of direct DNA binding.
  • These findings reveal a complex regulatory role for Stat5 in prolactin signaling pathways.

More Related Videos

Identification of MyoD Interactome Using Tandem Affinity Purification Coupled to Mass Spectrometry14:47

Identification of MyoD Interactome Using Tandem Affinity Purification Coupled to Mass Spectrometry

Published on: May 17, 2016

Prediction and Validation of Gene Regulatory Elements Activated During Retinoic Acid Induced Embryonic Stem Cell Differentiation09:07

Prediction and Validation of Gene Regulatory Elements Activated During Retinoic Acid Induced Embryonic Stem Cell Differentiation

Published on: June 21, 2016

Related Concept Videos

RNA Polymerase II Accessory Proteins02:36

RNA Polymerase II Accessory Proteins

Proteins that regulate transcription can do so either via direct contact with RNA Polymerase or through indirect interactions facilitated by adaptors, mediators, histone-modifying proteins, and nucleosome remodelers. Direct interactions to activate transcription is seen in bacteria as well as in some eukaryotic genes. In these cases, upstream activation sequences are adjacent to the promoters, and the activator proteins interact directly with the transcriptional machinery. For example, in...
Co-activators and Co-repressors02:04

Co-activators and Co-repressors

Gene transcription is regulated by the synergistic action of several proteins that form a complex at a gene regulatory site. This is observed in eukaryotes, where the regulation of gene expression is a complex process. Regulatory proteins in eukaryotes can broadly be classified into two types – regulators that bind directly to specific DNA sequences and co-regulators that associate with regulatory proteins but cannot directly bind to the DNA. These co-regulators are further divided into...
Master Transcription Regulators02:23

Master Transcription Regulators

Master transcription regulators are regulatory proteins that are predominantly responsible for regulating the expression of multiple genes. Often these genes work in concert to drive a  complex process. Activation of a master transcription regulator can lead to a cascade of transcriptional activation necessary for that outcome. These regulators can directly bind to the regulatory sequences of the various genes involved, or they can indirectly regulate transcription by binding to regulatory...
Co-activators and Co-repressors02:04

Co-activators and Co-repressors

Gene transcription is regulated by the synergistic action of several proteins that form a complex at a gene regulatory site. This is observed in eukaryotes, where the regulation of gene expression is a complex process. Regulatory proteins in eukaryotes can broadly be classified into two types – regulators that bind directly to specific DNA sequences and co-regulators that associate with regulatory proteins but cannot directly bind to the DNA. These co-regulators are further divided into...
Master Transcription Regulators02:23

Master Transcription Regulators

Master transcription regulators are regulatory proteins that are predominantly responsible for regulating the expression of multiple genes. Often these genes work in concert to drive a  complex process. Activation of a master transcription regulator can lead to a cascade of transcriptional activation necessary for that outcome. These regulators can directly bind to the regulatory sequences of the various genes involved, or they can indirectly regulate transcription by binding to regulatory...
Regulation of Expression at Multiple Steps01:23

Regulation of Expression at Multiple Steps

The gene expression in cells is regulated at different stages: (i) transcription, (ii) RNA processing, (iii) RNA localization, and (iv) translation. Transcriptional regulation is mediated by regulatory proteins such as transcription factors, activators, or repressors—these control gene expression by initiating or inhibiting the transcription of genes. Once a precursor or pre-mRNA is produced, it undergoes post-transcriptional modification, including 5' capping, splicing, and the addition of a...