The effect of oestradiol-17beta on the synthesis of uterine HnRNA and mRNA

Aziz, Shaharuddin (1979) The effect of oestradiol-17beta on the synthesis of uterine HnRNA and mRNA. PhD thesis, University of Glasgow.

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Evidence collected in this laboratory showed that an early action of oestrogen on the immature rat uterus was a dramatic stimulation in the synthesis of heterogenous nuclear RNA(HnRNA). Subsequently, mRNA, which is presumably derived from the HnRNA, accumulates in the cytoplasm and brings about the aggregation of pre-existing ribosomes into polysomes. This early response, and the translation of the mRNA into a small number of ill-characterized proteins, appears to be a prerequisite for the subsequent striking increase in synthesis of rRNA, the accumulation of new ribosomes and the subsequent uterine hypertroplay and hyperplasiao. The work in this thesis describes a continuing study of oestrogen-induced changes in uterine transcription and concentrates on 1) the effects of oestrogen on uterine HnRNA synthesis 2) the effect of oestrogen on the population of mRNA in uterine cell cytoplasm 3) the relationship of the HnRNA synthesis to the changes in mRNA diversity Uterine HnRNA was extensively purified and characterized under denaturing as well as non denaturing conditions. The purified high molecular weight HnRNA species were fractionated on poly(u) Sepharose into species differing in their poly(A) contento Each fraction was also found to differ in its size profile in polyacrylamide gels and sucrose gradients. Oestradiol treatment of the rats stimulated the synthesis of all three chromatographic fractions of high molecular weight HnRNA but the kinetics of synthesis, degree of stimulation and size distribution of the newly synthesized RNA differed in each fraction. The stimulation of HnRNA synthesis was detectable as early as 30 min after the administration of oestradiol and proceeded the synthesis of rRNA and the aggregation of ribosomes into polysomes. The stimulated synthesis of HnRNA at early times after oestradiol administration to immature rats was most striking in the polyadenylated fraction. Since evidence is accumulating that HnRNA contains polynucleotide sequences which ultimately become messengers, it is suggested that the stimulated production of this species in the uterus of oestrogen-stimulated rats may reflect hormone-induced mRNA synthesis. The diversity and complexity of the uterine poly(A)+mRNA population has been compared at two different stages of uterine growth and development in the rat. Analysis by cINA hybridization to homologous mRNA indicates that there are 8000 different sequences expressed in the immature rat uterus responding to just 4h of oestradiol-17beta induced growth while the fully developed uterus expresses 36,000 sequences. Reasons are discussed for believing that the analysis by this may lead to underestimates and for this reason and as a check on results obtained by cINA-RNA hybridization kinetics, the complexity was reanalysed by hybridization of mercurated mRNA to total unique 3H-labelled INA and hybridization assayed by thiol-Sepharose chromatography. Analysis by this method indicates that the hormone stimulated immature rat uterus contains 12,000 poly(A) containing mRNA sequences while the fully differentiated adult tissue contains 53,000 diverse sequences. The mRNA population of immature rat uteri, responding to different lengths of oestradiol-induced differentiation, have been compared by the technique of DNA hybridization with heterologous RNA. Over the first 4h of hormone-induction there are continuing qualitative and quantitative changes in the poly(A)+mRNA such that by 4h- after oestradiol treatment the population bears little resemblance to that of the unstimulated animal. Between 2h and 4h after oestradiol administration, the most striking changes are in sequences of intermediate abundance. The possible significance of these findings is discussed. cINA complementary to mRNA was separated into the abundant sequences by HAP chromatography and hybridized to oestradiol-stiraulated poly(A)+HhRNA. Hybridization data revealed the presence of mRNA sequences in poly(A)+HnRNA sedimenting at 40-30S under denaturing conditions. The mRNA sequence content increased several fold after 2h of oestradiol treatment.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J T Knower
Keywords: Endocrinology
Date of Award: 1979
Depositing User: Enlighten Team
Unique ID: glathesis:1979-72089
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:11
Last Modified: 24 May 2019 15:11

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