lncRNA BC200 is processed into a stable Alu monomer.

The noncoding RNA BC200 is elevated in human cancers and is implicated in translation regulation as well as cell survival and proliferation. Upon BC200 overexpression, we observed correlated expression of a second, smaller RNA species. This RNA is expressed endogenously and exhibits cell-type-dependent variability relative to BC200. Aptamer-tagged expression constructs confirmed that the RNA is a truncated form of BC200, and sequencing revealed a modal length of 120 nt; thus, we refer to the RNA fragment as BC120. We present a methodology for accurate and specific detection of BC120 and establish that BC120 is expressed in several normal human tissues and is also elevated in ovarian cancer. BC120 exhibits remarkable stability relative to BC200 and is resistant to knockdown strategies that target the 3' unique sequence of BC200. Combined knockdown of BC200 and BC120 exhibits greater phenotypic impacts than knockdown of BC200 alone, and overexpression of BC120 negatively impacts translation of a GFP reporter, providing insight into a potential translational regulatory role for this RNA. The presence of a novel, truncated, and stable form of BC200 adds complexity to the investigation of this noncoding RNA that must be considered in future studies of BC200 and other related Alu RNAs.