Locus Control Region Mechanism

[ecoli]

What I don't understand is how, in the intermediate stage, the assembly of the pre-initiation complex is only partially depended on the LCR.
In the next stage of LCR-dependent PIC assembly, is it the 'unknown' protein which binds to a complex of NF-E2 and the LCR that phosphorylates the C-terminal domain or RNAP?

(This is a question for my final exam on monday, btw)

(I have an image, btw, but I'm not allowed to post URLs yet.


(I have an accompanying image, but I'mnot allowed to post URLs yet).

[admin]

Hello this is a good review article I think:




http://www.nature.com/emboj/journal/.../7601654a.html

THere are a bunch of kinases that phosphorylate the CTD of RNAP here is an older paper:
http://ec.asm.org/cgi/content/full/1/2/153

But for the Beta globin gene: NF-E2 is recruited equally efficiently to the adult -globin promoters of the LCR and WT alleles. Moreover, the LCR deletion reduces PIC assembly only twofold, but has a dramatic effect on Ser 5 phosphorylation of RNA polymerase II and transcriptional elongation. Our results suggest at least three distinct stages in -globin gene activation: (1) an LCR-independent chromatin opening stage prior to NF-E2 recruitment to the promoter and PIC assembly; (2) an intermediate stage in which NF-E2 binding (LCR-independent) and PIC assembly (partially LCR-dependent) occur; and (3) an LCR-dependent fully active stage characterized by efficient pol II elongation. Thus, in its native location the LCR functions primarily downstream of activator recruitment and PIC assembly.


This is from http://www.genesdev.org/cgi/content/full/17/8/1009


For a more detailed review on phosphorylation of the CTD:
http://www.jbc.org/cgi/content/full/...e2=tf_ipsecsha


Figure 2. Schematic representation of the transcription cycle of RNAP II. Panel A shows a reaction scheme in which the formation of the preinitiation complex proceeds by the stepwise assembly of the GTFs and RNAP II onto the promoter. The CTD is represented by a heavy wavy line. CTDP, C-terminal domain phosphatase. Panel B shows a reaction scheme in which the holoenzyme is formed in the absence of DNA and loaded onto the promoter. The composition of the mediator and RNAP II holoenzyme has not been rigorously defined, especially in mammalian cells. Accordingly, even though specific GTFs are shown as constituents of the mediator or holoenzyme, this is for illustrative purposes only.

[ecoli]

Thanks... that's almost definitely more detail than I need for my exam, but Iwant to understand the completely mechanism, not just for my test!