Nucleus-specific linker histones Hho1 and Mlh1 form distinct protein interactions during growth, starvation and development in Tetrahymena thermophila

• Published in: Scientific reports Vol. 10; no. 1; p. 168
• Main Authors: Nabeel-Shah, Syed, Ashraf, Kanwal, Saettone, Alejandro, Garg, Jyoti, Derynck, Joanna, Lambert, Jean-Philippe, Pearlman, Ronald E., Fillingham, Jeffrey
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13.01.2020; Nature Publishing Group
• Subjects: 631/337/100; 631/337/176; 631/337/458; 631/337/475; Amino Acid Sequence; Animals; Cell Nucleus - genetics; Cell Nucleus - metabolism; Chromatin; Chromatin - genetics; Chromatin - metabolism; Gene expression; Gene Expression Regulation; Gene Expression Regulation, Developmental; Gene regulation; High Mobility Group Proteins - genetics; High Mobility Group Proteins - metabolism; Histone H1; Histones - metabolism; Humanities and Social Sciences; Life cycles; Mass spectrometry; Mass spectroscopy; MLH1 protein; multidisciplinary; MutL Protein Homolog 1 - genetics; MutL Protein Homolog 1 - metabolism; Protein interaction; Protein Interaction Domains and Motifs; Protein purification; Proteins; Proteome - analysis; Proteomics; Protozoa; Protozoan Proteins - genetics; Protozoan Proteins - metabolism; Science; Science (multidisciplinary); Starvation; Structure-function relationships; Tetrahymena; Tetrahymena thermophila; Tetrahymena thermophila - genetics; Tetrahymena thermophila - growth & development; Tetrahymena thermophila - metabolism
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-56867-0

Chromatin organization influences most aspects of gene expression regulation. The linker histone H1, along with the core histones, is a key component of eukaryotic chromatin. Despite its critical roles in chromatin structure and function and gene regulation, studies regarding the H1 protein-protein interaction networks, particularly outside of Opisthokonts, are limited. The nuclear dimorphic ciliate protozoan Tetrahymena thermophila encodes two distinct nucleus-specific linker histones, macronuclear Hho1 and micronuclear Mlh1. We used a comparative proteomics approach to identify the Hho1 and Mlh1 protein-protein interaction networks in Tetrahymena during growth, starvation, and sexual development. Affinity purification followed by mass spectrometry analysis of the Hho1 and Mlh1 proteins revealed a non-overlapping set of co-purifying proteins suggesting that Tetrahymena nucleus-specific linker histones are subject to distinct regulatory pathways. Furthermore, we found that linker histones interact with distinct proteins under the different stages of the Tetrahymena life cycle. Hho1 and Mlh1 co-purified with several Tetrahymena -specific as well as conserved interacting partners involved in chromatin structure and function and other important cellular pathways. Our results suggest that nucleus-specific linker histones might be subject to nucleus-specific regulatory pathways and are dynamically regulated under different stages of the Tetrahymena life cycle.