Interesting articles from different journals
Last issue of current biology reports an exciting find from the lab of Konrad Basler in Zurich ,where they demonstrate Transcription in the Absence of Histone H3.3. Normally methylation of histone H3 lysine 4 (H3K4me2 and H3K4me3) are indications of chromatin at active genes.Martina Hödl and Konrad Basler looked into this aspect into more details by by replacing wild-type H3.3 with a mutant form (H3.3K4A) that cannot be methylated. Studying the effects of mutant form of H3.3K4A in Drosophila ,authors looked into the transcription output in response to different signaling pathways. Surprisingly in mutant cells transcription of genes were uneffected and which lead them to conclude that in Drosophila, presence of H3.3K4me in the chromatin of active genes is dispensable for successful transcription in most cells and only plays an important role in reproductive tissues.
There was another article which caught my eye recently and want to share here is one from Plos Genetics. In this article McCutcheon et al deals with Origin of an Alternative Genetic Code in the Extremely Small and GC–Rich Genome of a Bacterial Symbiont. The cicada Diceroprocta semicincta is host to a highly unusual bacterial symbiont and feed exclusively on plant xylem sap. They need to take help of α-Proteobacteria, called Hodgkinia cicadicola to supplement their poor nutritional diet. This bacteria shows smallest reported genome of any cellular organism, with only 188 genes in total. Although all other small bacterial genomes are guanine-cytosine (GC)-poor, this one is GC-rich, resulting in an unprecedented combination of genomic features. Additionally, Hodgkinia uses an alternative genetic code, in which UGA has been reassigned from stop to tryptophan.
Reference :
1) Martina Hodi ,Konrad Basler
Transcription in the Absence of Histone H3.3
doi:10.1016/j.cub.2009.05.048
2) McCutcheon JP, McDonald BR, Moran NA (2009) Origin of an Alternative Genetic Code in the Extremely Small and GC–Rich Genome of a Bacterial Symbiont. PLoS Genet 5(7): e1000565. doi:10.1371/journal.pgen.1000565
Image Credit :
McCutcheon JP, McDonald BR, Moran NA (2009) Origin of an Alternative Genetic Code in the Extremely Small and GC–Rich Genome of a Bacterial Symbiont. PLoS Genet 5(7): e1000565.
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