Beyond the Identification of Transcribed
Sequences:
Functional and Expression Analysis
11th Annual Workshop
November 9-12, 2001
Washington D.C.
John Hesketh
Department of Biological and Nutritional Sciences,
University of Newcastle, Kings Rd.,
Newcastle-upon-Tyne, UK NE1 7RU
telephone: 44-191-222-8744
fax: 44-191-222-8684
email: j.e.hesketh@ncl.ac.uk
prestype: Platform
presenter: John Hesketh
John E. HESKETH and Marilyne LEVADOUX,
Department of Biological and Nutritional Sciences, University of Newcastle,
Newcastle-upon-Tyne, NE1 7RU, UK
Both c-myc and c-fos mRNAs are localised to the perinuclear cytoplasm and associated with the cytoskeleton and these mRNAs encode important nuclear transcription factors. The association of these mRNAs with the cytoskeleton and their perinuclear localisation is due to sequences within their 3’untranslated regions (e.g. Dalgleish et al., 2001). In addition the mRNA encoding metallothionein-1 (MT) is also associated with the cytoskeleton and localised around the nucleus. The MT mRNA is also targeted to the perinuclear cytoplasm and the cytoskeleton by signals within its 3’untranslated region (3’UTR). The localisation signal has not been exactly defined in any of these three mRNAs but it is relatively small (less than 86, 145 and 41nt in myc, fos and MT mRNAs respectively).
MT, which has a role in metal metabolism and may also protect DNA against oxidants, has been found localised in the nucleus during S-phase and has been suggested to play a role in apoptosis. Using cells transfected with gene constructs differing in their 3’UTRs we have investigated the role of perinuclear mRNA targeting in the facilitation of the subsequent import of MT into the nucleus and its function. Perinuclear localization of MT-1 mRNA and its association with the cytoskeleton was necessary for the shuttling of MT protein into the nucleus during the early S-phase (Levadoux et al., 1999). Following exposure of the cells to a variety of agents the extent of protection from oxidative stress and DNA damage provided by MT was lower if the mRNA was not correctly targeted. The data also suggest that MT plays a role in protecting cells against apoptosis (Levadoux-Martin et al., 2001).
Our hypothesis is that targeting of mRNA to the cytoskeleton around the nucleus is a mechanism which promotes the subsequent nuclear import of a range of proteins; in this way it contributes to local synthesis of the proteins close to their site of function.