Histone variant 3 regulates RNA polymerase II transcription termination and dual strand transcription of siRNA loci in Trypanosoma brucei

Histone variant 3 (H3V) is a kinetoplastid specific histone variant that is enriched at RNA polymerase II termination sites and telomeres. We previously found that the DNA modification base J, which co-localizes with H3V, functions to prevent readthrough transcription within gene clusters in T. brucei. We now demonstrate a similar role for H3V, where the loss of this histone variant results in increased expression of downstream genes. The effect is larger when both H3V and J are lost. Additionally, removal of H3V results in increased siRNAs from dual strand transcribed loci as well as increased expression of silent VSGs, indicating a role of H3V in the regulation of antigenic variation The role of H3V in regulating transcription termination was investigated using WT and H3V KO T. brucei cell lines. The role of J was also studied by treating each of these cell lines with DMOG, an inhibitor of J synthesis. We used 4 RNA seq libraries to determine gene expression changes following the loss of H3V and J