QuestionSBA
QuestionChoice
Transcription is up-regulated by enhancer elements which recruit enzymes such as p300, a histone acetylase which de-represses the target gene promoters that the sequences are folded to be adjacent to. Up-regulation of transcription does not involve Xist.
10001154
d
Up-regulation of transcription
QuestionChoice
In cells with multiple X-chromosomes, one chromosome expresses Xist, a long non-coding RNA which coats the X-chromosome from which it is expressed and recruits a polycomb repressive complex which uses EZH2 to catalyse H3K27me3 formation. This results in the recruitment of SETDB1 which catalyses the formation of H3K9me3. DNA methyltransferases then methylate the DNA, and laminin B receptors are recruited to anchor the newly condensed Barr body to the nuclear membrane.
10001151
a
X-inactivation
QuestionChoice
Genomic imprinting is the process by which a subset of genes is expressed in a parent-of-origin-specific manner. This is mediated by the differential methylation of imprinting control regions during epigenetic reprogramming in utero. Genomic imprinting does not involve Xist.
10001152
b
Genomic imprinting
QuestionChoice
Up-regulation of translation can be mediated by epi-transcriptomic changes. m6Adenine marks are the most common, added by METTL3/METTL14 at RRACH motifs. m6A binding proteins contain domains such as YTHDF2 which enhances mRNA translation. Up-regulation of translation does not involve Xist.

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10001155
e
Up-regulation of translation
QuestionChoice
Endogenous retroviruses are suppressed by specific KRAB zinc finger proteins binding to endogenous retroviral sequences and recruiting KAP1 to induce repressive chromatin remodelling using NuRD, HDAC and SETDB1. This promotes the methylation of endogenous retroviral promoters to repress transcription. piwi RNAs are also used during epigenetic reprogramming in germ cells and the blastocyst to prevent transcription when epigenetic markers are removed. Endogenous retrovirus suppression does not involve Xist.
10001153
c
Endogenous retrovirus suppression
Concept
Chapter
2693
3888
DNA
Topic
181
Structure and Function of Cells
12777
Xist, H3K27me3 and H3K9me3 are all associated with which process?
a