Nabeel-Shah S, Ashraf K, Saettone A, Garg J, Derynck J, Lambert JP, Pearlman RE, Fillingham J (2020) Nucleus-specific linker histones Hho1 and Mlh1 form distinct protein interactions during growth, starvation and development in Tetrahymena thermophila. Scientific reports 10(1):168 PUBMED:31932604
Akematsu T, Sánchez-Fernández R, Kosta F, Holzer E, Loidl J (2019) The Transmembrane Protein Semi1 Positions Gamete Nuclei for Reciprocal Fertilization in Tetrahymena. iScience 23(1):100749 PUBMED:31884169
Tian M, Loidl J (2019) An MCM family protein promotes interhomolog recombination by preventing precocious intersister repair of meiotic DSBs. PLoS genetics 15(12):e1008514 PUBMED:31815942
Identifiers and Description
Gene Model Identifier
TTHERM_00471820
Standard Name
MLH1 (Micronuclear Linker Histone )
Aliases
PreTt22590 | 56.m00294 | 3686.m00137
Description
Micronuclear linker histone polyprotein; contains linker histone peptides alpha, beta, delta and gamma; sequence not similar to typical histone H1; present in single copy in haploid genome
The HHO1 gene encodes the macronuclear linker histone H1 protein; the MLH1 gene encodes a polyprotein comprising a set of four micronuclear linker histone proteins (alpha, beta, gamma, and delta) unrelated to Hho1p. Histone H1 and the MLH proteins are chromatin proteins that associate with the inter-nucleosomal (linker) DNA. T. thermophila has two nuclei, one of which is transcriptionally active (the macronucleus) and one that is silent during most of the life cycle (the micronucleus). Furthermore, the macronucleus undergoes amitosis, whereas the micronucleus undergoes typical mitosis. The fact that Hho1p and MLH proteins are found exclusively in the macronucleus and micronucleus, respectively, has led to studies of their function, or lack of function, in transcription regulation, mitosis, and amitosis. Surprisingly, an HHO1 knockout showed this gene to be non-essential; its main observable phenotype was an overall decondensation of macronuclear chromatin. MLH1 knockouts, which are also viable, showed a similar phenotype in the micronucleus.
Associated Literature
Ref:31932604: Nabeel-Shah S, Ashraf K, Saettone A, Garg J, Derynck J, Lambert JP, Pearlman RE, Fillingham J (2020) Nucleus-specific linker histones Hho1 and Mlh1 form distinct protein interactions during growth, starvation and development in Tetrahymena thermophila. Scientific reports 10(1):168
Ref:29882620: Iwamoto M, Mori C, Osakada H, Koujin T, Hiraoka Y, Haraguchi T (2018) Nuclear localization signal targeting to macronucleus and micronucleus in binucleated ciliate Tetrahymena thermophila. Genes to cells : devoted to molecular & cellular mechanisms 23(7):568-579
Ref:8995382: Sweet MT, Carlson G, Cook RG, Nelson D, Allis CD (1997) Phosphorylation of linker histones by a protein kinase A-like activity in mitotic nuclei. The Journal of biological chemistry 272(2):916-23
Ref:8760889: Liu X, Gorovsky MA (1996) Cloning and characterization of the major histone H2A genes completes the cloning and sequencing of known histone genes of Tetrahymena thermophila. Nucleic acids research 24(15):3023-30
Ref:8947546: Sweet MT, Jones K, Allis CD (1996) Phosphorylation of linker histone is associated with transcriptional activation in a normally silent nucleus. The Journal of cell biology 135(5):1219-28
Ref:7606784: Shen X, Yu L, Weir JW, Gorovsky MA (1995) Linker histones are not essential and affect chromatin condensation in vivo. Cell 82(1):47-56
Ref:8264578: Wu M, Allis CD, Sweet MT, Cook RG, Thatcher TH, Gorovsky MA (1994) Four distinct and unusual linker proteins in a mitotically dividing nucleus are derived from a 71-kilodalton polyprotein, lack p34cdc2 sites, and contain protein kinase A sites. Molecular and cellular biology 14(1):10-20
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