ISSN:
0192-253X
Keywords:
sea urchin embryo
;
hnRNA
;
mRNA
;
5′ terminal cap
;
turnover
;
synthesis rate
;
methylation
;
developmental changes
;
Life and Medical Sciences
;
Genetics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
The relationship between heterogeneous nuclear RNA (hnRNA) and messenger RNA (mRNA) synthesis has been studied as a function of the development of the sea urchin embryo through the use of methyl incorporation. Several parameters in the metabolism of capped hnRNA and mRNA of early blastula and late gastrula stages have been investigated by measuring the kinetics of transfer of methyl groups from S-adenosylmethionine to the 5′ cap structures in nuclear and cytoplasmic RNA: 1The rate constants for the decay of hnRNA caps and the synthesis of mRNA caps are equal to within experimental error. This equality indicates a flux of precursor hnRNA caps to mRNA caps with a very high degree of conservation of the hnRNA caps. This conservation holds for each embryonic stage.2From literature data on the labeling kinetics of GTP and mRNA, we have calculated the decay constant of a putative mRNA precursor component of hnRNA. The value of this constant is very close to that for the decay constant of hnRNA caps. Hence, all hnRNA caps and some portion of their associated hnRNA sequences behave kinetically as the pre-mRNA fraction. This kinetically ascribed pre-mRNA comprises approximately 30% of the hnRNA mass.3The part of the hnRNA which does not serve as precursor to mRNA turns over at least twice as rapidly as the pre-mRNA fraction.4During development from early blastula to late gastrula, the rate of hnRNA cap synthesis drops from 2 × 103 molecules/min/cell to half of this value. This decline is parallel to the decline in total hnRNA synthesis and thereby confirms the constant degree of capping of hnRNA, as previously reported. We infer that the pre-mRNA fraction of hnRNA remains nearly constant during this developmental period.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/dvg.1020010204
