Tian M, Mochizuki K, Loidl J (2022) Arrested crossover precursor structures form stable homologous bonds in a Tetrahymena meiotic mutant. PloS one 17(2):e0263691 PUBMED:35171923
Nabeel-Shah S, Garg J, Saettone A, Ashraf K, Lee H, Wahab S, Ahmed N, Fine J, Derynck J, Pu S, Ponce M, Marcon E, Zhang Z, Greenblatt JF, Pearlman RE, Lambert JP, Fillingham J (2021) Functional characterization of RebL1 highlights the evolutionary conservation of oncogenic activities of the RBBP4/7 orthologue in Tetrahymena thermophila. Nucleic acids research ( ): PUBMED:34086947
Nabeel-Shah S, Garg J, Kougnassoukou Tchara PE, Pearlman RE, Lambert JP, Fillingham J (2021) Functional proteomics protocol for the identification of interaction partners in Tetrahymena thermophila. STAR protocols 2(1):100362 PUBMED:33786459
HHO1 knockouts show no global increase or decrease in the amount of transcription in the cell; however, these same knockouts also show that Hho1p is important for the transcriptional regulation of individual genes in response to stimuli, such as starvation. The differential regulation of Hho1p by phosphorylation under vegetative growth and starvation conditions has been well studied. During vegetative growth, Hho1p is phosphorylated on five closely spaced residues, preventing it from interacting with chromatin, likely by interfering with its ability to bind DNA. Under these conditions, expression is increased for CDC2, a homolog of the cyclin dependent kinases responsible for histone H1 phosphorylation, possibly creating a positive feedback loop that promotes the cell cycle. During starvation conditions, Hho1p is dephosphorylated, allowing it to bind to chromatin. This stimulates the expression of some genes, including ngoA, and protease genes such as CYP1, while inhibiting expression of other genes, such as CDC2. This decrease in CDC2 expression may be responsible for cell cycle arrest during starvation.
Associated Literature
Ref:17188762: Feng L, Miao W, Wu Y (2007) Differentially expressed genes of Tetrahymena thermophila in response to tributyltin (TBT) identified by suppression subtractive hybridization and real time quantitative PCR. Aquatic toxicology (Amsterdam, Netherlands) 81(1):99-105
Ref:11972045: Dou Y, Gorovsky MA (2002) Regulation of transcription by H1 phosphorylation in Tetrahymena is position independent and requires clustered sites. Proceedings of the National Academy of Sciences of the United States of America 99(9):6142-6
Ref:11891286: Shang Y, Song X, Bowen J, Corstanje R, Gao Y, Gaertig J, Gorovsky MA (2002) A robust inducible-repressible promoter greatly facilitates gene knockouts, conditional expression, and overexpression of homologous and heterologous genes in Tetrahymena thermophila. Proceedings of the National Academy of Sciences of the United States of America 99(6):3734-9
Ref:12356861: Dou Y, Bowen J, Liu Y, Gorovsky MA (2002) Phosphorylation and an ATP-dependent process increase the dynamic exchange of H1 in chromatin. The Journal of cell biology 158(7):1161-70
Ref:10207086: Huang H, Smothers JF, Wiley EA, Allis CD (1999) A nonessential HP1-like protein affects starvation-induced assembly of condensed chromatin and gene expression in macronuclei of Tetrahymena thermophila. Molecular and cellular biology 19(5):3624-34
Ref:8756729: Shen X, Gorovsky MA (1996) Linker histone H1 regulates specific gene expression but not global transcription in vivo. Cell 86(3):475-83
Ref:1996118: Dedon PC, Soults JA, Allis CD, Gorovsky MA (1991) Formaldehyde cross-linking and immunoprecipitation demonstrate developmental changes in H1 association with transcriptionally active genes. Molecular and cellular biology 11(3):1729-33
Ref:3005971: Martindale DW, Martindale HM, Bruns PJ (1986) Tetrahymena conjugation-induced genes: structure and organization in macro- and micronuclei. Nucleic acids research 14(3):1341-54
Ref:6646127: Martindale DW, Bruns PJ (1983) Cloning of abundant mRNA species present during conjugation of Tetrahymena thermophila: identification of mRNA species present exclusively during meiosis. Molecular and cellular biology 3(10):1857-65