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Published on: May 27, 2016
Molecular cloning and characterization of the human p19(INK4d) gene promoter
Youichirou Matsuzaki1, Kazuhiro Miyazawa, Tomoya Yokota
1Department of Preventive Medicine, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, Japan.
Abstract:
p19(INK4d), a member of the INK4 family of cyclin-dependent kinase (CDK) inhibitors, negatively regulates the cyclin D-CDK4/6 complexes, which promote G1/S transition by phosphorylating the retinoblastoma tumor-suppressor gene product. To investigate the mechanism of transcriptional regulation of the p19(INK4d) gene, we characterized the 5'-flanking region of the human p19(INK4d) gene. The cap-site hunting method revealed that the transcription starts at -16 nucleotide (nt) upstream of the initiation codon. The 5'-flanking region of the human p19(INK4d) gene was ligated to a luciferase reporter gene and possessed functional promoter activity. Luciferase assay with a series of truncated 5'-flanking regions indicated that the region from -81 to -2 nt could drive the transcription of the p19(INK4d) gene. Several Sp1 and activating protein 2 binding sites are located within the region from -81 to -2 nt. Mutation of the second Sp1 binding site from -33 to -25 nt decreased the promoter activity. Collectively, it was demonstrated that the human p19(INK4d) gene is under the control of TATA-less promoter and the Sp1 binding site is involved in the transcription.
Insights
The human p19(INK4d) gene, a cell cycle regulator, is controlled by a TATA-less promoter. Transcription initiation involves an Sp1 binding site within the promoter region, crucial for gene expression.
Area of Science:
- Molecular Biology
- Gene Regulation
- Cell Cycle Control
Background:
- p19(INK4d) is an inhibitor of cyclin D-CDK4/6 complexes, regulating cell cycle progression.
- Understanding the transcriptional regulation of p19(INK4d) is key to its role in cell cycle control.
Purpose of the Study:
- To investigate the transcriptional regulatory mechanisms of the human p19(INK4d) gene.
- To identify the functional promoter region and key regulatory elements involved in p19(INK4d) gene expression.
Main Methods:
- Cap-site hunting to determine the transcription start site.
- Reporter gene assays (luciferase) using truncated promoter constructs.
- Site-directed mutagenesis to assess the role of specific transcription factor binding sites.
Main Results:
- The transcription start site of the human p19(INK4d) gene was identified at -16 nucleotides relative to the initiation codon.
- The 5'-flanking region (-81 to -2 nt) exhibits functional promoter activity.
- An Sp1 binding site within this region is critical for driving p19(INK4d) transcription, and the promoter is TATA-less.
Conclusions:
- The human p19(INK4d) gene is regulated by a TATA-less promoter.
- Sp1 transcription factor binding sites are essential for the transcriptional activity of the p19(INK4d) gene promoter.
