Cell cycle-dependent transcription of CLN1 involves swi4 binding to MCB-like elements

Area of Science:

• Molecular Biology
• Yeast Genetics
• Cell Cycle Regulation

Background:

• Specific promoter elements regulate gene transcription during the G1/S phase in Saccharomyces cerevisiae.
• SCB elements are activated by Swi4-Swi6, and MCB elements by Mbp1-Swi6.
• The CLN1 gene requires Swi4 and Swi6 for transcription but lacks canonical SCB elements.

Purpose of the Study:

• To identify the functional promoter elements regulating G1/S-specific transcription of the CLN1 gene.
• To investigate the role of SCB-like and MCB-like sequences in CLN1 promoter activity.
• To characterize the DNA-binding specificities of transcription factors involved in CLN1 regulation.

Main Methods:

• Reporter gene assays (lacZ) to assess promoter activity.
• In vitro binding assays to determine Swi4-Swi6 complex interactions with DNA sequences.
• In vivo studies to evaluate the requirement of transcription factors for gene activity.

Main Results:

• Previously identified SCB-like sequences in the CLN1 promoter do not bind Swi4-Swi6 or activate transcription.
• A cluster of MCB-like sequences are the primary G1/S-specific regulatory elements in the CLN1 promoter.
• These MCB-like sequences bind Swi4-Swi6 and require Swi4 and Swi6 for activity, suggesting broader binding site definitions or alternative complexes.
• Novel promoter elements, distinct from SCB and MCB, also contribute to CLN1's cell cycle regulation.

Conclusions:

• The functional promoter elements for G1/S-specific transcription of CLN1 are primarily MCB-like sequences that bind Swi4-Swi6.
• These findings challenge the defined DNA-binding specificities for Swi4-Swi6 complexes.
• Additional, unidentified promoter elements are involved in the cell cycle-specific regulation of CLN1 transcription.