Biomedical subjects

Julien Häsler

Publications and source records attributed to Julien Häsler.

3 recordsLinked to original sources

PubMed2006

Alu elements as regulators of gene expression.

Alu elements are the most abundant repetitive elements in the human genome; they emerged 65 million years ago from a 5' to 3' fusion of the 7SL RNA gene and amplified throughout the human genome by retrotransposition to reach the present number of more than one million copies. Over the last years, several lines of evidence demonstrated that these elements modulate gene expression at the post-transcriptional level in at least three independent manners. They have been shown to be involved in alternative splicing, RNA editing and translation regulation. These findings highlight how the genome adapted to these repetitive elements by assigning them important functions in regulation of gene expression. Alu elements should therefore be considered as a large reservoir of potential regulatory functions that have been actively participating in primate evolution.

Alu Elements↗

PubMed2006

Alu RNP and Alu RNA regulate translation initiation in vitro.

Alu elements are the most abundant repetitive elements in the human genome; they emerged from the signal recognition particle RNA gene and are composed of two related but distinct monomers (left and right arms). Alu RNAs transcribed from these elements are present at low levels at normal cell growth but various stress conditions increase their abundance. Alu RNAs are known to bind the cognate proteins SRP9/14. We purified synthetic Alu RNP, composed of Alu RNA in complex with SRP9/14, and investigated the effects of Alu RNPs and naked Alu RNA on protein translation. We found that the dimeric Alu RNP and the monomeric left and right Alu RNPs have a general dose-dependent inhibitory effect on protein translation. In the absence of SRP9/14, Alu RNA has a stimulatory effect on all reporter mRNAs. The unstable structure of sRight RNA suggests that the differential activities of Alu RNP and Alu RNA may be explained by conformational changes in the RNA. We demonstrate that Alu RNPs and Alu RNAs do not stably associate with ribosomes during translation and, based on the analysis of polysome profiles and synchronized translation, we show that Alu RNP and Alu RNA regulate translation at the level of initiation.

Alu Elements↗

PubMed2003

Long term in vitro-cultured plant cells show typical neoplastic features at the cytological level.

Cells from a green normal (dependent on exogenous hormones) callus and from an achlorophyllous fully habituated (independent from exogenous hormones) callus, both generated from the same sugarbeet strain more than twenty years ago, were reexamined cytologically, ten years after the first comparative description. Cells from the habituated callus, already considered as neoplastic cells, because terminating a neoplastic progression where the organogenic totipotency was lost, still showed nuclear invaginations, polynucleolation, vacuolation of nucleoli and incomplete cell walls, nevertheless at a higher degree. The present study particularly shows that, compared to their previous description, normal cells have started to acquire some features (polynucleolation, nuclear invaginations.) that are typical of the neoplastic cells. This suggests that normal cells, on the long term, also entered a neoplastic progression, which should explain the known progressive loss of regeneration capacity of too long subcultured hormone-dependent calli.

Beta vulgaris↗