Present two lines of evidence that argue against the holoenzyme recruitment model.

Name: Problem 16, Chapter 12: Molecular Biology
Uploaded: 2021-04-24T22:28:36-08:00
Duration: 5 min 46 s
Channel: Eric Goldman
Description: Present two lines of evidence that argue against the holoenzyme recruitment model.

Present two lines of evidence that argue against the...

Key Concepts

Post-Recruitment Regulation and Alternative Mechanisms

Evidence against a strictly recruitment-based mechanism comes from observations that gene activation can be modulated without significant changes in holoenzyme association at the promoter. This suggests that regulatory steps following recruitment, such as transitions in the transcriptional machinery (for instance, promoter clearance, polymerase pausing, or elongation control), can be major determinants of transcription levels. This concept underscores the importance of post-recruitment events and kinetic control in transcription regulation.

Holoenzyme Recruitment Model

This concept refers to a model of transcription activation in which sequence?specific activators function by directly binding and recruiting the RNA polymerase holoenzyme, along with general transcription factors, to the promoter. In this framework, the formation of the preinitiation complex at the promoter is thought to occur chiefly by the physical assembly of the enzyme complex at that site as a consequence of activator interactions.

Transcript

00:01 For this question, we're looking at dna transcription and the role of certain proteins involved with it, including the nucleosome octomers.

00:09 We also have the protein h1, and during this experiment they're looking at a special protein called galfour, vp16.

00:19 So here we can start by taking a look at dna transcription and the role of octomers and this h1 histone protein.

00:27 So of course dna is going to be in that double -stranded structure, and you're going to have special regions associated with it.

00:36 You're going to have a promoter region, and you can also have certain repressor and other regions involved with this.

00:47 The role of octomers and the h1 histone protein is to raffle up this double -stranded dna in order to condense it so it can fit in the nucleus.

00:58 And you're going to have two kind of confirmations of the histone proteins.

01:03 You have a methylated form where you have methyl groups attached to the dna and the histone proteins, and you have an acetylated form.

01:17 And there you have acetyl groups attached to your histone proteins.

01:21 And those are going to affect the way that your dna wraps around those histones.

01:26 So in your methylated form, dna is going to be closely wound to eat.

01:31 Each of the histone proteins and you're going to have very little space in between.

01:37 In the acetylated form, it's going to be in a looser confirmation and you'll have much more space in between each of your histones.

01:46 And this is going to affect the way your genes can be read.

01:50 So of course, inside of that dna, we have those genes of interest.

01:55 But in order to transcribe these genes, we need polymerases and other proteins able to...

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