SRA

Circadian clocks generate endogenous rhythms in most organisms from cyanobacteria to humans and facilitate entrainment to environmental diurnal cycles, thus conferring a fitness advantage. Both transcriptional and posttranslational mechanisms are prominent in the basic network architecture of circadian systems. Posttranscriptional regulation, including mRNA processing, is emerging as a critical step for the clock function. However, little is known about the molecular mechanisms linking RNA metabolism to the circadian clock network. Here we report that a conserved SNW/SKIP domain protein, SKIP, a splicing factor and component of the spliceosome, is involved in the posttranscriptional regulation of circadian clock genes in Arabidopsis. Mutation in SKIP lengthens the circadian period in a temperature sensitive manner, affects light input and the sensitivity of light resetting to the clock. SKIP physically interacts with the spliceosomal splicing factor SR45 and associates with the pre-mRNA of clock genes, such as PRR7 and PRR9, and is necessary for the regulation of their alternative splicing and mRNA maturation. Genome-wide investigations reveal that SKIP functions in regulating alternative splicing of many genes, presumably through modulating recognition or cleavage of 5' and 3' splicing site. Our study addresses a fundamental question on how the mRNA splicing machinery contributes to circadian clock functions at a posttranscriptional level. Overall design: Our findings revealed that AtSKIP is a splicing factor and a component of spliceosome. To further investigate effects of mutation in SKIP on the genome-wide changes of alternative splicing, we performed ultra-highthroughput RNA sequencing, using 10-day old seedlings. Two biological replicates for both wild type (Col-0) and skip-2 were designed.