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Protein inhibitors of activated STAT resemble scaffold attachment factors and function as interacting nuclear
Jiann-An Tan1, Susan H Hall, Katherine G Hamil
1Laboratories for Reproductive Biology, Department of Pediatrics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7500, USA.
Abstract:
Protein inhibitor of activated STAT1 (PIAS1) functions as a nuclear receptor coregulator and is expressed in several cell types of human testis. However, the mechanism of PIAS1 coregulation is unknown. We report here that PIAS1 has characteristics of a scaffold attachment protein. PIAS1 localized in nuclei in a speckled pattern and bound A-T-rich double-stranded DNA, a function of scaffold attachment proteins in chromatin regions of active transcription. DNA binding was dependent on a 35-amino acid sequence conserved among members of the PIAS family and in scaffold attachment proteins. The PIAS family also bound the androgen receptor DNA binding domain, and binding required the second zinc finger of this domain. PIAS1 contained an intrinsic activation domain but had bi-directional effects on androgen receptor transactivation; lower expression levels inhibited and higher levels increased transactivation in CV1 cells. Other PIAS family members also had dose-dependent effects on transactivation, but they were in a direction opposite to those of PIAS1. When coexpressed with PIAS1, other PIAS family members counteracted PIAS1 coregulation of androgen receptor transactivation. The interaction of PIAS1 with other members of the PIAS family suggests a transcription coregulatory mechanism involving a multicomponent PIAS nuclear scaffold.
Insights
Protein inhibitor of activated STAT1 (PIAS1) acts as a nuclear scaffold protein. PIAS1 binds DNA and the androgen receptor, influencing gene transcription in a dose-dependent manner.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Protein inhibitor of activated STAT1 (PIAS1) is a nuclear receptor coregulator found in human testis.
- The precise mechanism of PIAS1 coregulation remains largely undefined.
Purpose of the Study:
- To elucidate the mechanism of PIAS1 coregulation.
- To investigate PIAS1's role as a scaffold attachment protein and its interaction with the androgen receptor.
Main Methods:
- Localization studies of PIAS1 within the nucleus.
- DNA binding assays to identify PIAS1's DNA-binding sequence.
- Androgen receptor binding assays.
- Transactivation assays to assess PIAS1's effect on gene expression.
Main Results:
- PIAS1 exhibits characteristics of a scaffold attachment protein, localizing to nuclei with a speckled pattern.
- PIAS1 binds A-T-rich double-stranded DNA via a conserved 35-amino acid sequence.
- PIAS1 binds the androgen receptor's DNA binding domain, specifically requiring the second zinc finger.
- PIAS1 demonstrated bi-directional effects on androgen receptor transactivation, with dose-dependent inhibition at lower levels and activation at higher levels.
- Other PIAS family members showed opposing dose-dependent effects and could counteract PIAS1's coregulation.
Conclusions:
- PIAS1 functions as a nuclear scaffold protein with DNA-binding capabilities.
- PIAS1's interaction with the androgen receptor and its dose-dependent regulatory effects highlight its complex role in transcription.
- The interplay between PIAS1 and other PIAS family members suggests a multicomponent nuclear scaffold mechanism for transcription coregulation.