Intracellular communication of genetic information in mammalian cells

Katinakis, Panagiotis (1979) Intracellular communication of genetic information in mammalian cells. PhD thesis, University of Glasgow.

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Utilising the technique of poly(A)-sepharose affinity chromatography, it has proven possible to isolate a class of RNA from polysomes of Friend leukaemia cells, clone M2, which does not appear to be of ribosomal origin since its synthesis is unaffected by concentrations of actinomycin D (0.04mug/ml) which inhibit rRNA synthesis. Although this class displays messenger-like behaviour in being released from polysomes on treatment with EDTA and in being able to direct polypeptide synthesis in a cell-free system it is nonetheless distinct from the well-known polyadenylated messenger RNAs (poly(A)+mRNAs) as judged by the following properties - (a) A complete lack of poly(A) tracts (b) A different size distribution on denaturing gradients, displaying a mean size of 20s compared to 18s for polyCA)+ RNAs. (c) The presence, close to the 3' terminus, of an "uridylate- rich" region in contrast to the 3'-poly(A) tracts of the poly (A)+RNA. (d) Little sequence homology with poly(A)+RWAs as judged from molecular hybridisation data. (e) A different base composition compared to poly(A)+RNA. (f) In contrast to poly(A)+RNA which is transcribed from both unique and middle-repetitive DNA sequences, this new class of RNA seems to be transcribed solely from unique sequences. (g) A difference in metabolic stability between this class and the poly(A)+RM class was found. (h) The size distribution of polypeptide products pro-duced when this RNA is used as template in a cell-free protein synthesising system appears slightly different to that directed by poly(A)+mRNA. The lack of poly(A) tracts coupled with the presence of "U-rich" region(s) has led to the designation of this class of RM as poly(A)-u+RNA. In addition to detecting these poly(A)-u+RNAs in polysomes, a similar class of RWAs have also been detected in nuclei. The nuclear poly(A)-U+RNAS. elute from poly(A)-sepharose with increasing formamide concentration in a similar fashion to that of the polysomal poly (A)-u+RNAs. Indeed, the "U-rich" region(s) of nuclear and polysomal poly(A)-u+RNAs appear similar. In a further examining of the total nuclear RNA, two other RNA classes having either poly(A) tracts (poly(A)+RNA) or oligo(A) tracts (poly(A)-a+RNA) were also detected. These three RNA classes display distinct size distribution and content of double-stranded regions. When the stability of these nuclear RWA classes were examined, using a "pulse-chase" approach, it was found that the poly(A)-u+RNA class was relatively labile compared to the poly(A)+RNA. Interestingly, the poly(A)+RNA appeared to have at least two distinct metabolic components. The "pulse-chase" approach used, allowed an estimate to be made of the conversion of nuclear poly(A)+ and poly(A)-u+ RNAs into cytoplasmic poly(A)+and poly (A)-u+RNAs . Finally the metabolic behaviour of both the nuclear and cytoplasmic classes of RNA was found to be relatively unaffected by induction of Friend cells using Dimethylsulphoxide.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: R H Burdon
Keywords: Biochemistry
Date of Award: 1979
Depositing User: Enlighten Team
Unique ID: glathesis:1979-73415
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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