Transcription of genetic information in amphibian oocytes

Sommerville, John; Malcolm, D. B.

doi:10.1007/bf01798348

Cited by 56 publications

(29 citation statements)

References 46 publications

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“…19,24,95 For example, only about 1.2% and 3% of transcribed sequences on the Xenopus and Triturus lateral loops serve as mRNA. 91,98 In contrast, mRNAs content in the ooplasm of other metazoan representatives ranged from 35% to 65%, with a large part of mRNAs possibly eliminated later. 94 The majority of RNA species represent transcripts of repetitive sequences, including tandem repeats, 95 indicating that their non-coding RNAs are not just waste products of read-through transcription.…”

Section: Functions Of the Non-coding Tandemly Repetitive Dna Transcrimentioning

confidence: 98%

“…[90][91][92][93][94][95][96][97][98] However, mRNAs represents only a small fraction of RNAs synthesized in amphibian or avian oocytes, with some of the housekeeping genes being inactive at the lampbrush stage of oogenesis. 19,24,95 For example, only about 1.2% and 3% of transcribed sequences on the Xenopus and Triturus lateral loops serve as mRNA.…”

Section: Functions Of the Non-coding Tandemly Repetitive Dna Transcrimentioning

confidence: 99%

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Transcription of highly repetitive tandemly organized DNA in amphibians and birds: A historical overview and modern concepts

Trofimova

Krasikova

2016

RNA Biology

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Tandemly organized highly repetitive DNA sequences are crucial structural and functional elements of eukaryotic genomes. Despite extensive evidence, satellite DNA remains an enigmatic part of the eukaryotic genome, with biological role and significance of tandem repeat transcripts remaining rather obscure. Data on tandem repeats transcription in amphibian and avian model organisms is fragmentary despite their genomes being thoroughly characterized. Review systematically covers historical and modern data on transcription of amphibian and avian satellite DNA in somatic cells and during meiosis when chromosomes acquire special lampbrush form. We highlight how transcription of tandemly repetitive DNA sequences is organized in interphase nucleus and on lampbrush chromosomes. We offer LTR-activation hypotheses of widespread satellite DNA transcription initiation during oogenesis. Recent explanations are provided for the significance of high-yield production of non-coding RNA derived from tandemly organized highly repetitive DNA. In many cases the data on the transcription of satellite DNA can be extrapolated from lampbrush chromosomes to interphase chromosomes. Lampbrush chromosomes with applied novel technical approaches such as superresolution imaging, chromosome microdissection followed by high-throughput sequencing, dynamic observation in life-like conditions provide amazing opportunities for investigation mechanisms of the satellite DNA transcription.

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Section: Functions Of the Non-coding Tandemly Repetitive Dna Transcrimentioning

confidence: 98%

Section: Functions Of the Non-coding Tandemly Repetitive Dna Transcrimentioning

confidence: 99%

Transcription of highly repetitive tandemly organized DNA in amphibians and birds: A historical overview and modern concepts

Trofimova

Krasikova

2016

RNA Biology

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“…The lampbrush chromosomes of amphibian oocytes are the sites of intense transcriptional activity (1). Although the RNA sequences present in oocytes have been partially characterized, many questions remain to be answered (2)(3)(4). One important question is the extent to which the oocyte sequences are specific for oogenesis and early development.…”

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confidence: 99%

Presence of tadpole and adult globin RNA sequences in oocytes of Xenopus laevis

Perlman

Ford

Rosbash

1977

Proc. Natl. Acad. Sci. U.S.A.

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The swimming tadpole, which possesses an active circulatory system, was also assayed for the tadpole and adult globin sequences. Whereas the adult sequences are present at approximately the same concentration as in the mature oocyte, the concentration of the tadpole sequences increases at least 300-fold in the first 3 days following fertilization. The lampbrush chromosomes of amphibian oocytes are the sites of intense transcriptional activity (1). Although the RNA sequences present in oocytes have been partially characterized, many questions remain to be answered (2-4). One important question is the extent to which the oocyte sequences are specific for oogenesis and early development.One approach to this problem is to assay ovary RNA for mRNA sequences that code for proteins normally associated with terminally differentiated cells. In this report, a successful search for the globin mRNA sequence of Xenopus laevis in the oocyte is described. In addition, the number of copies of this sequence per oocyte was found to be not markedly different from the number of copies of the&majority of other poly(A)-containing sequences per oocyte.MATERIALS AND METHODS Preparation of RNA. Ovary RNA. Ovaries were removed from mature X. laevis females, washed with Barth X medium (5), and resuspended in Barth X medium containing 1% Pronase and 25 mM EDTA. After 10-15 min, the individual oocytes were essentially free of follicle cells. In some experiments, the oocytes were separated according to size as described (2). The oocytes were washed and the RNA was extracted by the method of Kirby as described (2, 6).Egg RNA. Unfertilized ovulated eggs were dejellied with Barth X containing 2% cysteine (7 (12). were synthesized and purified as described except that [32P]dCTP was used at a final concentration of 32 IiM (13).RNA-DNA Hybridization and Assay. RNA-DNA hybridization was performed as described (14) except that the reactions were at 70°in 1.0 M NaCI/5 mM EDTA/10 mM Tris-HCI, pH 7.4. Crot (product of RNA concentration and time in mol-sec/liter) values were determined in one of two ways. For total RNA, Crot was determined from the optical density by assuming 1 mg = 25 A260 units. For poly(A)-containing RNA, the amount of poly(A) was determined by hybridization with radioactive poly(U) (15). Poly(A)-containing RNA from the tadpole, oocyte, and egg was assumed to have a length of 1500 nucleotides and a 5% poly(A) content. The Crot values were corrected to 0.18 M Na+ at 600 (Crote) as described (13,16). Hybrid formation was monitored with nuclease SI as described (13).Abbreviations: cDNA, complementary DNA; Crot, product of RNA concentration and time in mol-sec/liter; Crote, Crot corrected to 0.18 M Na+ at 600.

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“…(15) There is reasonable correspondence, subject to problems arising from different genome sizes and uncertainty about the amount of DNA in the axis of a lampbrush loop, between the complexity of conserved transcripts and the proportion of the genomic DNA that is in the loops at the stage of maximum lampbrush development (Sommerville and Malcolm, 1976).…”

Section: Lampbrush Chromosomes 25mentioning

confidence: 99%

Recent developments in the study of lampbrush chromosomes

Macgregor

1980

Heredity

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M brief in writing this essay is to provide a state-of-the-art review about research into the organisation and function of the lampbrush chromosomes that are found in the growing oocytes of amphibians, The task is likely to be pleasurable, since lampbrushology is a field of research that offers wide horizons and innumerable challenges. Within this field, the questions remain clear and the challenges manageable. As from the very beginning all we have to do is sort out our reasoning, take advantage of what Nature has to offer, steady our hands, and get on with the job.My starting point is a paper written in 1975 (Macgregor, 1977) in which I attempted to summarise the history of lampbrush studies and focused on two major questions. The first concerned the functional significance of a lampbrush loop. The second question concerned the nature of a lampbrush chromomere and its associated loops in molecular terms. At the time, the answers were difficult to find. In the matter of function I concluded that there was widespread transcription of many DNA sequences on the lateral loops of lampbrush chromosomes. The primary transcript was large. Only a small part of it was retained, and apart from clearly repetitive sequences such as the ribosomal, 5S, and histone genes, the retained material was transcribed from single copies. This explanation fitted with most of the available evidence in 1975. rt did not tell us anything about regulation of transcription, and it did not explain the fact that a set of lampbrush chromosomes may have as many as 5000 chromomeres, all of which bear ioops that are transcriptionally active at the same time. In particular, I concluded that Callan's spinning out and retraction hypothesis (Callan and Lloyd, 1960;Gall and Callan, 1962;Snow and Callan, 1969) in which he sought to explain the shape of an average lampbrush loop, its relationship with its chromomere and its extension and retraction during oogenesis, was open to question and further experimentation. Essentially, the problem of movement of the DNA loop axis and its associated RNP product, or movement of the RNP transcript over the stationary loop axis was unresolved. As we shall see later, the clear solution of this particular problem represents one of the major steps forward of the past 5 years.With regard to chromomeres, the scarcity of hard data imposed rather strict limits on speculation. I suggested in 1975 that chromomeric material was essentially heterochromatic in the same general sense that a chromocentre is heterochromatic, and that it owed its compactness to a commonness in the sequences of its DNA. I represented an average chromomere as a gathering together of a stretch of DNA that was rich in a particular repetitive 3

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Transcription of genetic information in amphibian oocytes

Cited by 56 publications

References 46 publications

Transcription of highly repetitive tandemly organized DNA in amphibians and birds: A historical overview and modern concepts

Transcription of highly repetitive tandemly organized DNA in amphibians and birds: A historical overview and modern concepts

Presence of tadpole and adult globin RNA sequences in oocytes of Xenopus laevis

Recent developments in the study of lampbrush chromosomes

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