PAR-TERRA directs homologous sex chromosome pairing

@article{Chu2017PARTERRADH,
  title={PAR-TERRA directs homologous sex chromosome pairing},
  author={Hsueh-Ping Chu and John E Froberg and Barry A. Kesner and Hyun Jung Oh and Fei Ji and Ruslan I. Sadreyev and Stefan F. Pinter and Jeannie T. Lee},
  journal={Nature structural \& molecular biology},
  year={2017},
  volume={24},
  pages={620 - 631}
}
In mammals, homologous chromosomes rarely pair outside meiosis. One exception is the X chromosome, which transiently pairs during X-chromosome inactivation (XCI). How two chromosomes find each other in 3D space is not known. Here, we reveal a required interaction between the X-inactivation center (Xic) and the telomere in mouse embryonic stem (ES) cells. The subtelomeric, pseudoautosomal regions (PARs) of the two sex chromosomes (X and Y) also undergo pairing in both female and male cells. PARs… 

Nuclear positioning and pairing of X-chromosome inactivation centers are not primary determinants during initiation of random X-inactivation

TLDR
It is found that neither nuclear lamina localization nor reduction of Xic homologous pairing influences monoallelic Xist upregulation or choice-making, and transient pairing is associated with biallelic expression, not only at Xist/Tsix but also at other X-linked loci that can escape XCI.

Characterization of telomeric repeat-containing RNA (TERRA) localization and protein interactions in primordial germ cells of the mouse†.

TLDR
The data indicate that TERRA expression and interactome during PGC development are regulated in a dynamic fashion that is dependent on gestational age and sex.

Revisiting the consequences of deleting the X inactivation center

TLDR
The essential nature of noncoding Xic elements for the initiation of XCI is reaffirmed, as multiple independent clones carrying heterozygous deletions of the Xic display an inability to up-regulate Xist expression, consistent with a counting defect.

PAR-TERRA is the main contributor to telomeric repeat-containing RNA transcripts in normal and cancer mouse cells.

TLDR
It is shown that PAR-TERRA molecules account for the majority of TERRA transcripts, displaying an increase of 2 to 4 orders of magnitude compared to the telomeric 18q transcript, and a large overlap between TERRA-interacting proteins in human and mouse cells is presented.

Characterization of Telomeric Repeat-Containing RNA (TERRA) localization and protein interactions in Primordial Germ Cells of the mouse

TLDR
The results show that, TERRA interacting proteins are determined by sex in both PGCs and somatic cells, and indicate that TERRA expression and interactome during PGC development are regulated in a dynamic fashion that is dependent on gestational age and sex.

Gene regulation in time and space during X-chromosome inactivation

TLDR
The multiple layers of genetic and epigenetic regulation that underlie initiation of XCI during development and then maintain it throughout life are discussed, in light of the most recent findings in this rapidly advancing field.

Megadomains and superloops form dynamically but are dispensable for X-chromosome inactivation and gene escape

TLDR
Evidence is provided that megadomains do not precede Xist expression or Xi gene silencing, and it is suggested that Dxz4, Firre, and megadamains are dispensable for Xi silencing and escape from X-inactivation.

Decapping enzyme 1A breaks X-chromosome symmetry by controlling Tsix elongation and RNA turnover

TLDR
“BioRBP” is developed, an enzymatic RNA-proteomic method that enables probing of low-abundance interactions and an allelic RNA-depletion and -tagging system and reports that DCP1A negatively regulates Tsix RNA abundance by suppressing its transcriptional elongation and RNA stability, thus contributing to X-chromosome inactivation.

The Emerging Roles of TERRA in Telomere Maintenance and Genome Stability

TLDR
Emerging evidence indicates that a class of long noncoding RNAs transcribed at telomeres, known as TERRA for “TElomeric Repeat-containing RNA,” actively participates in the mechanisms regulating telomere maintenance and chromosome end protection.

DNA–RNA interactions are critical for chromosome condensation in Escherichia coli

TLDR
It is demonstrated that naRNA4 uniquely acts by forming complexes that may not involve long stretches of DNA–RNA hybrid, which will be of great interest in the chromatin field, providing mechanistic insights into the large-scale organization of DNA.

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