Trithorax-group proteins

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Trithorax-group proteins (TrxG) are a heterogeneous collection of proteins whose main action is to maintain gene expression. They can be categorized into three general classes based on molecular function:

  1. histone-modifying TrxG proteins
  2. chromatin-remodeling TrxG proteins
  3. DNA-binding TrxG proteins,

plus other TrxG proteins not categorized in the first three classes.[1]

Discovery

The founding member of TrxG proteins, trithorax (trx), was discovered ~1978 by Philip Ingham as part of his doctoral thesis while a graduate student in the laboratory of J.R.S. Whittle at the University of Sussex.[2] Histone-lysine N-methyltransferase 2A is the human homolog of trx.[2]

Members of Trithorax Group Proteins:
Name Symbol(s)
absent, small or homeotic discs 1 ash1
absent, small or homeotic discs 2 ash2
brahma brm
Brahma associated protein 55kD Bap55
Brahma associated protein 60 kD Bap60
dalao dalao
domino dom
Enhancer of bithorax E(bx)
enhancer of yellow 3 SAYP or e(y)3
eyelid eld or osa
female sterile (1) homeotic fs(1)h
grappa gpp
Imitation SWI Iswi
kismet kis
little imaginal discs lid
lola like lolal
modifier of mdg 4 mod(mdg4), E(var)3-93D, or doom
moira mor
Nucleosome remodeling factor-38kD Nurf38
trithorax trx
Trithorax like Trl
Ubiquitously transcribed tetratricopeptide repeat, X chromosome Utx
verthandi vtd
zeste z

The table contains names of Drosophila TrxG members. Homologs in other species may have different names.

Function

Trithorax-group proteins typically function in large complexes formed with other proteins. The complexes formed by TrxG proteins are divided into two groups: histone-modifying complexes and

gene activation. The trithorax complex activates gene transcription by inducing trimethylation of lysine 4 of histone H3 (H3K4me3) at specific sites in chromatin recognized by the complex.[1] Ash1 domain is involved in H3K36 methylation. Trithorax complex also interacts with CBP (CREB binding protein) which is an acetyltransferase to acetylate H3K27.[3] This gene activation is reinforced by acetylation of histone H4. The actions of TrxG proteins are often described as 'antagonistic' of PcG proteins function.[4] Aside from gene regulation, evidence suggests TrxG proteins are also involved in other processes including apoptosis, cancer, and stress responses.[5][6][7]

Role in development

During development, TrxG proteins maintain activation of required genes, particularly the

embryogenesis.[10] As of 2011 it is unclear whether TrxG activity is required in every cell during the entire development of an organism or only during certain stages in certain cell types.[11]

See also

References

  1. ^
    PMID 17320510
    .
  2. ^
    PMID 9654027
    .
  3. PMID 26329598
    .
  4. S2CID 19504262
    .
  5. PMID 19763085
    .
  6. PMID 20018689
    .
  7. PMID 17289567
    .
  8. PMID 15704101
    .
  9. PMID 21290568
    .
  10. PMID 20150277
    .
  11. S2CID 19992445
    .

External links
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