Chromatin Structure Part 3 Flashcards Preview

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Flashcards in Chromatin Structure Part 3 Deck (20):

chromosome looping

- how chromatin divided into functional domains within the nucleus
- forms loops and condenses a lot



- Boundaries between domain of the gene and the enhancer (or silencer)
- the gene can no longer feel the activating (or repressing) effects


domain boundaries

- special nucleoprotein structures formed by proteins at specific sites along the chromosome


how is inappropriate activation avoided?

- organisms use DNA insulators to block activation of unrelated genes by nearby enhancers


insulator proteins

- recruit histone acetyltransferases that acetylate flanking nucleosomes
- inhibits histone modifications required for the propagation of transcriptionally silent condensed chromatin
- prevents spread of heterochromatic DNA


boundary elements

- relate structural organization of chromatin fiber into informational organization of the DNA


position effects

- when genes relocated to new chromosomal environments by rearrangement or transformation
- modifies gene expression


in vivo assay for boundary function

- determine if DNA sequences can protect a reporter gene from chromosomal position effects


the site of insertion

- helps determine the level of expression of the transgene


chromatin looping between elements facilitates transcription at submegabase level

- initiation of transcription involves physical interaction between gene regulatory elements such as promoters and enhancers
- may be separated by many kilo bases along the linear chromosome
- DNA loops out so enhancer can interact with promoter to initiate transcription


topically associated domains (TADs)

- chromosomes are further segregated into these containing many chromatin loops
- separated by architectural proteins at their borders


architectural proteins (APs)

- bend DNA and allow formation of loops
- also function as insulators


chromosome territories (CTs)

- TADs further organized at entire chromosome level, forming these
- non randomly organized in the nucleus and occupy distinct regions


lamin-associated domains (LADs)

- nucleus further segmented into different compartments


repression facilitated by

- associated of genomic sequences with the inner nuclear lamina through lamin binding proteins
- gene position toward periphery of nucleus generally results in transcriptional repression


transcriptional neighborhoods (TNs)

- contain a collection of transcriptional machinery
- provide an environment for initiation and hyper activation and maintenance of transcription
- multiple genes and regulatory elements founds within TNs


directed chromatin movement

- local compaction of chromatin by architectural proteins
- looping out of specific genomic regions


local compaction of chromatin by architectural proteins

- permits interaction between specific promoters and enhancers
- bend DNA into topological domains
- enables transcription of specific genes


looping out of specific genomic regions

- to form long-range interactions with distal enhancers requires some chromatin slack
- decompact neighboring region
- previously interacting enhancer/promoter loops sacrificed to permit new loops
- allows interaction with promoters on different chromosomes


domains are dynamic

- change under development time or physiological conditions to allow for change in gene expression