The Saccharomyces cerevisiae TRT2 tRNAThr gene upstream of STE6 is a barrier to repression in MATalpha cells and exerts a potential tRNA position effect in MATa cells.
A growing body of evidence suggests that genes transcribed by RNA polymerase III exhibit multiple functions within a chromosome. While the predominant function of these genes is the synthesis of RNA molecules, certain RNA polymerase III genes also function as genomic landmarks. Transfer RNA genes are known to exhibit extra-transcriptional activities such as directing Ty element integration, pausing of replication forks, overriding nucleosome positioning sequences, repressing neighboring genes (tRNA position effect), and acting as a barrier to the spread of repressive chromatin. This study was designed to identify other tRNA loci that may act as barriers to chromatin-mediated repression, and focused on TRT2, a tRNA(Thr) adjacent to the STE6 alpha2 operator. We show that TRT2 acts as a barrier to repression, protecting the upstream CBT1 gene from the influence of the STE6 alpha2 operator in MATalpha cells. Interestingly, deletion of TRT2 results in an increase in CBT1 mRNA levels in MATa cells, indicating a potential tRNA position effect. The transcription of TRT2 itself is unaffected by the presence of the alpha2 operator, suggesting a hierarchy that favors assembly of the RNA polymerase III complex versus assembly of adjacent alpha2 operator-mediated repressed chromatin structures. This proposed hierarchy could explain how tRNA genes function as barriers to the propagation of repressive chromatin.
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
Tiffany A
TA
Simms
Elsy C
EC
Miller
Nicolas P
NP
Buisson
Nithya
N
Jambunathan
David
D
Donze
D018528:ATP-Binding Cassette Transporters; D015825:Chromosomes, Fungal; D005656:Fungal Proteins / Q000235:genetics; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D005800:Genes, Fungal; D006023:Glycoproteins; D006657:Histones / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics; D009875:Operator Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D012363:RNA, Transfer, Thr / Q000096:biosynthesis / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic
D018528:ATP-Binding Cassette Transporters; C109121:CBT1 protein, S cerevisiae; D005656:Fungal Proteins; D006023:Glycoproteins; D006657:Histones; D018398:Homeodomain Proteins; C062928:MATA2 protein, S cerevisiae; D012333:RNA, Messenger; D012363:RNA, Transfer, Thr; D012097:Repressor Proteins; C489277:STE6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins