Cell cycle-dependent transcription of CLN1 involves swi4 binding to MCB-like elements.
Two promoter elements have been defined that activate G1/S-specific transcription in Saccharomyces cerevisiae. SCB elements (CACGAAA) are activated by the Swi4-Swi6 complex, and MCB elements (ACGCGTNA) are activated by the Mbp1-Swi6 complex. CLN1 encodes a cyclin which is expressed during this interval, and requires Swi4 and Swi6 for peak transcription, but it has no consensus SCB elements in its promoter. Two SCB-like sequences had been previously noted and suggested to be the functional promoter elements. Our studies indicate that these sequences are unable to activate transcription of a lacZ reporter construct, or to bind Swi4-Swi6 complexes in vitro. However, a cluster of three sequences resembling MCB sequences are active promoter elements, sufficient to confer G1/S-specific transcription to a reporter. These sites are the predominant activation elements in the CLN1 promoter, and despite their resemblance to MCB elements, they bind Swi4-Swi6 complexes in vitro and require Swi4 and Swi6 for their activity in vivo. This indicates that the sequences that promote Swi4/Swi6 binding have not been fully defined, or that there are multiple Swi4- and Swi6-containing complexes with distinct DNA binding specificities. In addition to these novel Swi4/Swi6-binding sites, these studies also show that there must be at least one novel promoter element that can confer G1/S-specific transcription to CLN1, because when all the potential SCB- and MCB-like sequences are eliminated the transcript is still cell cycle regulated.
Partridge
J F
JF
Fred Hutchinson Cancer Research Center, Basic Sciences Division, Seattle, Washington 98104, USA.
Mikesell
G E
GE
Breeden
L L
LL
D002453:Cell Cycle; D016213:Cyclins / Q000096:biosynthesis* / Q000235:genetics; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015719:Single-Strand Specific DNA and RNA Endonucleases / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic
C082719:CLN1 protein, S cerevisiae; D016213:Cyclins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C062214:SWI4 protein, S cerevisiae; C075111:SWI6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D015719:Single-Strand Specific DNA and RNA Endonucleases