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Gene Review

MED4  -  mediator complex subunit 4

Homo sapiens

Synonyms: ARC36, Activator-recruited cofactor 36 kDa component, DRIP36, HSPC126, Mediator complex subunit 4, ...
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Disease relevance of MED4

  • Analysis of a metagenomic library from the Sargasso Sea supports this hypothesis; most Prochlorococcus cells in this low-P environment contain the P-acquisition genes seen in MED4, although a number of previously undescribed gene combinations were observed [1].
  • Heterologous expression of the two cloned P. marinus MED4 ppa genes in Escherichia coli confirmed this proposal, only the inactive ppa1 product being immunodetected by anti-cyanobacterial sPPase antibodies [2].
  • The latter represents an intermediate form between the phycobiliproteins of non-Chl b containing cyanobacteria and an extremely modified beta phycoerythrin as the sole derivative of phycobiliproteins still present in MED4 [3].

High impact information on MED4

  • Previous analyses of the differences in pigmentation and gene complement revealed that LL-adapted ecotypes carry a gene cluster to produce a functional phycoerythrin, whereas in the fully sequenced genome of the HL-adapted strain MED4, only a single and free-standing cpeB gene occurs [4].
  • We observed that MED4 and SS120 have lost several DNA-repair genes, the absence of which could be related to the mutational bias and the acceleration of amino-acid substitution [5].
  • In keeping with their comparative light-dependent physiologies, MED4 has many more genes encoding putative high-light-inducible proteins (HLIP) and photolyases to repair UV-induced DNA damage, whereas MIT 9313 possesses more genes associated with the photosynthetic apparatus [3].

Analytical, diagnostic and therapeutic context of MED4

  • First, we used DNA microarrays to identify genes involved in the P-starvation response in two strains belonging to different ecotypes, MED4 (high-light-adapted) and MIT9313 (low-light-adapted) [1].


  1. Phosphate acquisition genes in Prochlorococcus ecotypes: evidence for genome-wide adaptation. Martiny, A.C., Coleman, M.L., Chisholm, S.W. Proc. Natl. Acad. Sci. U.S.A. (2006) [Pubmed]
  2. Expression studies of two paralogous ppa genes encoding distinct Family I pyrophosphatases in marine unicellular cyanobacteria reveal inactivation of the typical cyanobacterial gene. Gómez-García, M.R., Serrano, A. Biochem. Biophys. Res. Commun. (2002) [Pubmed]
  3. The photosynthetic apparatus of Prochlorococcus: Insights through comparative genomics. Hess, W.R., Rocap, G., Ting, C.S., Larimer, F., Stilwagen, S., Lamerdin, J., Chisholm, S.W. Photosyn. Res. (2001) [Pubmed]
  4. Analysis of natural populations of Prochlorococcus spp. in the northern Red Sea using phycoerythrin gene sequences. Steglich, C., Post, A.F., Hess, W.R. Environ. Microbiol. (2003) [Pubmed]
  5. Accelerated evolution associated with genome reduction in a free-living prokaryote. Dufresne, A., Garczarek, L., Partensky, F. Genome Biol. (2005) [Pubmed]
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