Dictyate

The dictyate or dictyotene[1] is a prolonged resting phase in oogenesis. It occurs in the stage of meiotic prophase I[2] in ootidogenesis. It starts late in fetal life[2] and is terminated shortly before ovulation by the LH surge.[3] Thus, although the majority of oocytes are produced in female fetuses before birth, these pre-eggs remain arrested in the dictyate stage until puberty commences and the cells complete ootidogenesis.

In both mouse and human, oocyte DNA of older individuals has substantially more double-strand breaks than that of younger individuals.[4]

The dictyate appears to be an adaptation for efficiently removing damages in germ line DNA by homologous recombinational repair.[5]

Translation halt

There are a lot of mRNAs that have been transcribed but not translated during dictyate.[6] Shortly before ovulation, the oocyte of interest activates these mRNA strains.

Biochemistry mechanism

Translation of mRNA in dictyate is partly explained by molecules binding to sites on the mRNA strain, which results in that initiation factors of translation can not bind to that site. Two such molecules, that impedes initiation factors, are CPEB and maskin, which bind to CPE (cytoplasmic polyadenylation element). When these two molecules remain together, then maskin binds the initiation factor eIF-4E,[6] and thus eIF4E can no longer interact with the other initiation factors[7] and no translation occurs. On the other hand, dissolution of the CPEB/maskin complex leads to eIF-4E binding to the initiation factor eIF-4G,[6] and thus translation starts, which contributes to the end of dictyate and further maturation of the oocyte.

See also

References

  1. ↑ Medical Physiology, Boron & Boulpaep, ISBN 1-4160-2328-3, Elsevier Saunders 2005. Updated edition. 1300 pages.
  2. 1 2 Thomas, Richard D, ed. (1986). Drinking Water and Health 6. Washington, D.C.: National Academies Press. p. 35. ISBN 0-309-03687-9.
  3. ↑ 'Hormones and Mammalian Egg Maturation', Michael Barresi, http://8e.devbio.com/article.php?id=275, Accessed 15 Apr 08 1613
  4. ↑ Titus S, Li F, Stobezki R, Akula K, Unsal E, Jeong K, Dickler M, Robson M, Moy F, Goswami S, Oktay K (2013). "Impairment of BRCA1-related DNA double-strand break repair leads to ovarian aging in mice and humans". Sci Transl Med 5 (172): 172ra21. doi:10.1126/scitranslmed.3004925. PMID 23408054.
  5. ↑ Harris Bernstein, Carol Bernstein and Richard E. Michod (2011). Meiosis as an Evolutionary Adaptation for DNA Repair. Chapter 19 in DNA Repair. Inna Kruman editor. InTech Open Publisher. DOI: 10.5772/25117 http://www.intechopen.com/books/dna-repair/meiosis-as-an-evolutionary-adaptation-for-dna-repair
  6. 1 2 3 Molecule.org - Maskin Is a CPEB-Associated Factor that Transiently Interacts with eIF-4E Barbara Stebbins-Boaz,1 Quiping Cao,1 Cornelia H de Moor,1 Raul Mendez,1 and Joel D Richter1
  7. ↑ Lodish 2008, p.351


This article is issued from Wikipedia - version of the Sunday, August 02, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.