Essay - Genetics Article Summary 'Histones Face the Facts' According to the...

genetics

***** Summary "Histones Face the Facts"

According to the article entitled, "Histones Face the Facts," the "beads on a string" nature of eukaryotic chromatin poses a difficult quandary for scientists, in the case of RNA polymerase II complex, or *****P *****. How can this complex efficiently transcribe a cod*****g region that is tightly wrapped in nucleosomes and why does it do so?

Three recently published papers by scientists provide several key insights into the mechanisms and fact*****s that enable transcription to take place through this chromatin, explaining why it ***** not have to become nucleosome free for transcription to occur.

***** papers, respectively published Kaplan et al. and Belotserkovskaya et *****. and Saunders et al. provide detail how the his*****ne chaperone activ*****y of the elongation factors Spt6 and FACT enables the dissociation ***** histone proteins in front of RNAPII and their immediate reassociation with the DNA in its wake. Results from ***** work of *****, Laprade and Winston demonstrate that an spt 6 mutation impairs the integrity of chromatin in active genes.

***** et *****.***** data strongly suggest that chromatin reassembly after passage of the polymerase is defective in cells lacking ***** activity, thus ***** why RNA polymerase replicates in ***** fashion ***** it does.

Secondly, *****, Reinberg, ***** colleagues report that FACT ***** capable of promoting transcription dependent *****s alterations, and that this factor also facilitates assembly of histone ***** into nucleosomes in vitro even in the absence of RNAPII. So these results are consistent with the idea that ***** enables chromat***** structure to be disrupted and then reestablished during transcription. This model is lastly supported by ***** ***** *****, Lis, and co-workers showing that FACT is associated ***** actively transcribed RNAPII genes on Drosophila polytene chromosomes, ***** that its kinetics of associati***** and site of action are consistent with its involvement in transcript ***** through chromatin. ***** has the intrinsic ability to disassemble nucleosomes ***** *****ion.

In combination, all ***** *****se studies suggest that the app*****ntly impossible technique of RNAPII is enabled through RNAP II's ability to ***** nucleosomes ***** ***** use ***** ***** in transcript elongation. Interest*****gly enough RNAP III is not ***** of this process, pointing ***** new, possible areas of research in the