Proteomic Analysis of Core Histones and Their Variants in Tetrahymena Thermophila

Several histone chaperones including Nasp, Asf1, Caf1 and Hira have been identified to function in the transport and assembly of newly synthesized histones. To characterize histone transport machinery and chromatin assembly proteins in ciliate protozoan Tetrahymena thermophila, I used affinity purification combined with mass spectrometry to identify protein-protein interactions of core histone H2A, variants Hv1 and H3.3 as well as linker histone MLH1. I found that H2A co-purifies with putative Spt16Tt and Pob3Tt subunits of the T. thermophila FACT complex. Proteomic analysis of Hv1 indicated that it co-purifies with an Importinβ3, suggesting a possible mechanism of targeting Hv1 specifically to transcriptionally active macronucleus. My data also indicated that H2A, Hv1 and H3.3 co-purify with putative PARP1 and PARP2 proteins suggesting that ribosylation of histones might have a critical role in the chromatin maintenance.