Allshire lab paper featured in eLife. Image In this study, we identified the composition and characterised the function of SPARC - a novel protein complex which associates with RNAPII promoters in Trypanosoma brucei. Our results show that SPARC is required for accurate RNAPII positioning and transcription initiation and, in some instances, correct transcription directionality. Authors Staneva, D.P., Bresson, S., Auchynnikava, T., Spanos, C., Rappsilber, J., Jeyaprakash, A.A., Tollervey, D., Matthews, K.R., and Allshire, R.C. Summary of Paper by Lori Koch Kinetoplastids are a group of organisms that are highly different from most other eukaryotes and so have developed interesting unique mechanisms of regulating gene expression. The kinetoplastid parasite Trypanosoma brucei can be carried through the tse tse fly and pass sleeping sickness to humans. Previous research from PhD student Desi Staneva in the Allshire Lab identified factors associated with chromatin in T. brucei. They found that the lysine methyltransferase SET27 and the chromodomain protein CRD1 were associated with the 5’ end of genes. In their recent paper published in eLife, Desislava and colleagues identify that these proteins form a complex together with 4 other proteins that localizes to gene promoters. They named the complex SPARC for SET27 promoter-associated regulatory complex. They identified the 4 other members of the complex using an immunoprecipitation followed by mass spectrometry method, first in the blood-stream form of T. brucei and then also in the insect-stage form. Using ChIP-sequencing, they found that all 6 proteins SET27, CRD1, CSD1, PHD6, PBP1, and PWWP1 are found at the 5’ ends of genes and co-localize with RNA polymerase II in promoters. Next they created T. brucei cell lines lacking SET27 (set27∆/∆) and RNA sequencing showed that the genes expressed in these cells were significantly different from normal, with many silent or weakly expressed genes becoming expressed. By ChIP-seq they could see that the position of RNA polymerase II was shifted compared to normal conditions, suggesting that the SPARC complex is required for correct transcription start site positioning. Intriguingly the genes that are aberrantly up-regulated in set27∆/∆ cells were within 2.5kb of the normal position of the SPARC complex, whereas this distance was much larger (~65kb) for an average, unchanged gene. Overall, their study suggests that the SPARC complex is required for the identification of gene promoters in T. brucei. Related links Journal Link Allshire Lab Website DOI This article was published on 2024-06-17
