TGD | Gene Details

Identifiers and Description

Gene Model Identifier
TTHERM_00823720

Standard Name
HHO1 (Histone H One )

Aliases
PreTt20442 | 141.m00099 | 3682.m00033

Description
Histone H1; macronuclear linker histone that associates with inter-nucleosomal DNA; lacks globular domain typical of linker histones; five phosphorylation

Genome Browser

Gene Ontology Annotations

Cellular Component
macronucleus (TAS) | GO:0031039 | Ref:8760889
Biological Process
negative regulation of transcription from RNA polymerase II promoter (IMP) | GO:0000122 | Ref:8756729
positive regulation of transcription from RNA polymerase II promoter (IMP) | GO:0045944 | Ref:8756729
chromatin organization (IMP) | GO:0006325 | Ref:7606784

Domains

( PF07554 ) Uncharacterised Sugar-binding Domain

Gene Expression Profile

Tetrahymena Functional Genomics Database: TTHERM_00823720

Homologs (v.2006 protein sequences)

No Data fetched for Homologs

General Information

Paragraph No Gene Name Paragraph Text
8 HHO1,
MLH1 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.
9 HHO1,
CDC2,
NgoA,
CYP1 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

No Data fetched for Associated Literature

Sequences

>TTHERM_00823720(coding)
ATGGCTCCCAGAAGTTCAACTTCCAAGTCTGCTACCAGAGAAAAGAAGGACCACAAGAAG
GCTCCCATCAAGAAAGCCATCGCCAAGAAGGATACTAAGCCTACCCCCACCAAGGGCAAG
GCTGCTTCTGCTTCCACCACCCCCGTCAAGAAGGATGTCACCCCCGTCAAGGCTGATACC
AAGAAGAAGATCCACAAAACCAAAACCATGAAGGAAACCGTCAGCGATGCCAAGAAGACC
GTTCACGCTGCTGCTGGTGATAAGAAGCTCTCTAAAAAGAGACCCGCTAAGGAAGCTGCT
AAGAAGGCTATCAACCCTGGTAAGAAGGCTGCTGCTTAACCCAAGAGCACCAAGAAGGAA
GTTAAGAAGGACAATAAGACTGCCAAGAAGGAAACCAAGAAAGATCATAAGCCCGCTAAG
AAGGAAGCTAAGAAGGAAACCAAGCCTGCCAAGAAAGATGCCAAGAAGAGCTCCAAGCCT
GCCAAGAAGAACTGA

>TTHERM_00823720(protein)
MAPRSSTSKSATREKKDHKKAPIKKAIAKKDTKPTPTKGKAASASTTPVKKDVTPVKADT
KKKIHKTKTMKETVSDAKKTVHAAAGDKKLSKKRPAKEAAKKAINPGKKAAAQPKSTKKE
VKKDNKTAKKETKKDHKPAKKEAKKETKPAKKDAKKSSKPAKKN

>TTHERM_00823720(gene)
AAATTAAATCGTTAAGAAAAAAACAAGAAAAAAAAACTAAAAAACAAATAATATAAAATG
GCTCCCAGAAGTTCAACTTCCAAGTCTGCTACCAGAGAAAAGAAGGACCACAAGAAGGCT
CCCATCAAGAAAGCCATCGCCAAGAAGGATACTAAGCCTACCCCCACCAAGGGCAAGGCT
GCTTCTGCTTCCACCACCCCCGTCAAGAAGGATGTCACCCCCGTCAAGGCTGATACCAAG
AAGAAGATCCACAAAACCAAAACCATGAAGGAAACCGTCAGCGTAAGAATTTAACGATTT
GTTTCTACTATTTTCATTAAATAAATTCAAAATAGAATTTTTAATTACTAAATACTTTCT
CCTCCTTTGGTTATTTATTGAAGTTTCTACTATTTTTAAGAAACATATTTTAATAGTTCT
ACACTTTTTTTCTCACTAAAAGAGAGTTAAAAAGTAGAATGAATGAATTAATACAAATAT
TATTGGGAAAAACGTTTTATTCATTTTATTGAAAATATCTTTAATTTAAAAATTAGGATG
CCAAGAAGACCGTTCACGCTGCTGCTGGTGATAAGAAGCTCTCTAAAAAGAGACCCGCTA
AGGAAGCTGCTAAGAAGGCTATCAACCCTGGTAAGAAGGCTGCTGCTTAACCCAAGAGCA
CCAAGAAGGAAGTTAAGAAGGACAATAAGACTGCCAAGAAGGAAACCAAGAAAGATCATA
AGCCCGCTAAGAAGGAAGCTAAGAAGGAAACCAAGCCTGCCAAGAAAGATGCCAAGAAGA
GCTCCAAGCCTGCCAAGAAGAACTGATTTTTTTGTAGTAAAGAAATTCCTCAAAATACTC
ACATTCACAAGAGAAGAGACTTGATATGAGCAAGTGATCAAAAGGCTTTAAAGGGAGGTA
ATTAAAAAAATGAATTCTCTTAGGCTGGAAGAAATCAAGTTCTATACAATATTTTCTCAA
GTGAAATGTAGAGTAGATGTTAATATAAAATATAATAATAAAAGGGTTATGAATCATCAA
AAATGCACACTCAACGAGTGTAAAAATGTATATATATCTTCTTAATCATTAAATATATTG
GTATATAATAATCAACTTTTACTACTAACAAGAAGCAGATAAATCCTTTATTGACTTAAA
TTTATTTATGTATATGTTCTGCATACAATGAATGTGTATTCCTTGATGATTTGATAGAGT
TTATCATTAA

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Identifiers and Description

Gene Model Identifier

Standard Name

Aliases

Description

Genome Browser

Gene Ontology Annotations

Cellular Component

Biological Process

Domains

Gene Expression Profile

Homologs (v.2006 protein sequences)

General Information

Associated Literature

Sequences

Wiki Links

External Links

Paragraph No	Gene Name	Paragraph Text
8	HHO1, MLH1	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.
9	HHO1, CDC2, NgoA, CYP1	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.