Ectopic expression of pericentric HSATII RNA results in nuclear RNA accumulation, MeCP2 recruitment, and cell division defects

Abstract

Within the pericentric regions of human chromosomes reside large arrays of tandemly repeated satellite sequences. Expression of the human pericentric satellite HSATII is prevented by extensive heterochromatin silencing in normal cells, yet in many cancer cells, HSATII RNA is aberrantly expressed and accumulates in large nuclear foci in cis. Expression and aggregation of HSATII RNA in cancer cells is concomitant with recruitment of key chromatin regulatory proteins including methyl-CpG binding protein 2 (MeCP2). While HSATII expression has been observed in a wide variety of cancer cell lines and tissues, the effect of its expression is unknown. We tested the effect of stable expression of HSATII RNA within cells that do not normally express HSATII. Ectopic HSATII expression in HeLa and primary fibroblast cells leads to focal accumulation of HSATII RNA in cis and triggers the accumulation of MeCP2 onto nuclear HSATII RNA bodies. Further, long-term expression of HSATII RNA leads to cell division defects including lagging chromosomes, chromatin bridges, and other chromatin defects. Thus, expression of HSATII RNA in normal cells phenocopies its nuclear accumulation in cancer cells and allows for the characterization of the cellular events triggered by aberrant expression of pericentric satellite RNA.

A classical revival: Human satellite DNAs enter the genomics era

“…They found that lncRNAs from HSat2, but not from αSat, accumulated in visible foci and recruited MeCP2 in cis with the transgene. Furthermore, they found that ectopic satellite expression resulted in segregation defects [154]. These results suggest that the formation of nuclear stress bodies and chromosome instability phenotypes in cancer cells result directly from aberrant satellite transcription rather than some other property of cancer.…”

“…HSat2/3 lncRNAs play a role in recruiting splicing factors and other proteins such as MeCP2 to nuclear stress bodies [136,[150][151][152], and they are associated with mitotic segregation defects [153]. A recent study examined these phenomena further by stably expressing ectopic HSat2 lncRNAs from a transgene randomly integrated into a primary human fibroblast line [154]. They found that lncRNAs from HSat2, but not from αSat, accumulated in visible foci and recruited MeCP2 in cis with the transgene.…”

Sequence, Chromatin and Evolution of Satellite DNA

“…When protein-coding genes are juxtaposed to pericentric heterochromatin due to genomic rearrangements, they undergo silencing in some somatic cells but not in others, a phenomenon called position-effect variegation (PEV) [ 219 , 220 , 221 ]. Human pericentric satellites are silenced in normal cells but are aberrantly expressed in many cancer cells, which coincides with the accumulation of methyl-CpG binding protein 2 at pericentromeres [ 222 , 223 ]. Pericentromeric satellites assemble highly condensed constitutive heterochromatin, which once established during development, remains permanently condensed during interphase.…”

A Classical Revival: Human Satellite DNAs Enter The Genomics Era

“…They found that lncRNAs from HSat2, but not from αSat, accumulated in visible foci and recruited MeCP2 in cis with the transgene. Furthermore, they found that ectopic satellite expression resulted in segregation defects (Landers et al 2021). These results suggest that the formation of nuclear stress bodies and chromosome instability phenotypes in cancer cells result directly from aberrant satellite transcription rather than some other property of cancer.…”

“…HSat2/3 lncRNAs play a role in recruiting splicing factors and other proteins such as MeCP2 to nuclear stress bodies (Aly et al 2019, Hall et al 2017, Ninomiya et al 2020, and they are associated with mitotic segregation defects (Giordano et al 2020). A recent study examined these phenomena further by stably expressing ectopic HSat2 lncRNAs from a transgene randomly integrated into a primary human fibroblast line (Landers et al 2021). They found that lncRNAs from HSat2, but not from αSat, accumulated in visible foci and recruited MeCP2 in cis with the transgene.…”