Divisão celular requer nível equilibrado de RNA não codificante para estabilidade cromossômica: mero acaso, fortuita necessidade ou design inteligente?

sábado, maio 25, 2019

Point centromere activity requires an optimal level of centromeric noncoding RNA

Yick Hin Ling and Karen Wing Yee Yuen

PNAS March 26, 2019 116 (13) 6270-6279; first published March 8, 2019 https://doi.org/10.1073/pnas.1821384116

Edited by Douglas Koshland, University of California, Berkeley, CA, and approved February 5, 2019 (received for review December 21, 2018)

Fig. 5.
Fig. 5 Knockdown of total cenRNAs reduces mitotic stability of minichromosome.


Budding yeast harbors a simple point centromere, which is originally believed to be sequence dependent without much epigenetic regulation and is transcription incompatible, as inserting a strong promoter upstream inactivates the centromere completely. Here, we demonstrate that an optimal level centromeric noncoding RNA is required for budding yeast centromere activity. Centromeric transcription is induced in S phase, coinciding with the assembly of new centromeric proteins. Too much or too little centromeric noncoding RNA leads to centromere malfunction. Overexpression of centromeric noncoding RNA reduces the protein levels and chromatin localization of inner centromere and kinetochore proteins, such as CENP-A, CENP-C, and the chromosome passenger complex. This work shows that point centromere is epigenetically regulated by noncoding RNA.


In budding yeast, which possesses simple point centromeres, we discovered that all of its centromeres express long noncoding RNAs (cenRNAs), especially in S phase. Induction of cenRNAs coincides with CENP-ACse4 loading time and is dependent on DNA replication. Centromeric transcription is repressed by centromere-binding factor Cbf1 and histone H2A variant H2A.ZHtz1. Deletion of CBF1 and H2A.ZHTZ1 results in an up-regulation of cenRNAs; an increased loss of a minichromosome; elevated aneuploidy; a down-regulation of the protein levels of centromeric proteins CENP-ACse4, CENP-A chaperone HJURPScm3, CENP-CMif2, SurvivinBir1, and INCENPSli15; and a reduced chromatin localization of CENP-ACse4, CENP-CMif2, and Aurora BIpl1. When the RNA interference system was introduced to knock down all cenRNAs from the endogenous chromosomes, but not the cenRNA from the circular minichromosome, an increase in minichromosome loss was still observed, suggesting that cenRNA functions in trans to regulate centromere activity. CenRNA knockdown partially alleviates minichromosome loss in cbf1Δ, htz1Δ, and cbf1Δ htz1Δ in a dose-dependent manner, demonstrating that cenRNA level is tightly regulated to epigenetically control point centromere function.

centromeric transcription long noncoding RNA centromere-binding factor Cbf1 histone H2A variant Htz1 chromosome instability