2019 journal article

Cohesin SA2 and EWSR1 in R-Loop Regulation

Biophysical Journal, 116(3), 505a.

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Added: January 25, 2020

R-loops are three-stranded nucleic acid structures consisting of an RNA-DNA hybrid and a displaced single-stranded DNA (ssDNA) loop. R-loops collectively occupy up to 5% of the mammalian genome, which occur at conserved hotspot including promoter and terminator regions of poly(A) dependent genes. R-loops are proposed to be the "double-edged sword" that functions as powerful regulators of gene expression and induces genome instability if it is un-regulated. Despite the importance of R-loops in a wide range of biological pathways, proteins that mediate R-loop dependent cellular function are not fully understood. Recently The Bishop group showed that Ewing sarcoma cells displayed a higher level of R-loops compared to control cell lines. EWSR1 depletion induces R-loop accumulation. In addition, the second most common mutation in Ewing sarcoma cells was found in cohesin SA2. These observations raise the important question of whether EWSR1 as well as cohesin SA1 and SA2 subunits are sensors of R-loops that regulate R-loop processing. Using atomic force microscopy (AFM) and bulk fluorescence anisotropy, we tested the hypothesis that cohesin SA1, SA2, and EWSR1 directly bind to R-loops. We observed that cohesin SA1/SA2, and EWSR1 specifically recognize R-loops. These observations suggest direct roles of cohesin SA1/SA2 and EWSR1 in R-loop regulation and how the loss of SA2 in Ewing sarcoma may provide some benefit to these cancers.