(This is a guest post by Ana Pena, who is the first author of Trypanosoma brucei histone H1 inhibits RNA polymerase I transcription and is important for parasite fitness in vivo, a paper I had a small hand in).
The organization of DNA inside the eukaryotic nucleus relies on what we like to call the “beads-on-a-string” structure of chromatin, in which nucleosomes are the “beads” and DNA is the “string” around. While we already know a lot about the histones that make up the nucleosome, the functions of the “extra” histone, histone H1, only now start to be uncovered in vivo.
Histone H1 is a small protein that sits outside the nucleosome “beads” and binds to the DNA between them. In this work we explored the role of histone H1 in Trypanosoma brucei, a unicellular parasite responsible for Sleeping Sickness. Genome-wide RNA expression revealed an interesting fact in this parasite: histone H1 acts mainly as a repressor of a particular cohort of genes, which are transcribed by RNA polymerase I and are essential for its differentiation and survival inside the host. To understand if histone H1 represses transcription at these loci, we performed metabolic labeling of nascent RNAs with 4sU for the first time in this parasite, showing that histone H1 silencing effect is exerted at the transcriptional level.
Full paper citation
Pena AC, Pimentel MR, Manso H, Vaz-Drago R, Neves D, Aresta-Branco F, Ferreira FR, Guegan F, Coelho LP, Carmo-Fonseca M, Barbosa-Morais NL, Figueiredo LM. “Trypanosoma brucei histone H1 inhibits RNA polymerase I transcription and is important for parasite fitness in vivo”. Mol Microbiol, 2014 Jun 19. doi: 10.1111/mmi.12677.