Stability of MALAT-1, a nuclear long non-coding RNA in mammalian cells, varies in various cancer cells

Recent large-scale transcriptome analyses have revealed a large number of transcripts with low protein-coding potential, known as non-coding RNAs (ncRNAs). Many studies revealed that several long ncRNAs are involved in the regulation of genome organization and gene expression, or in the structural components of functional domains in the nucleus. As regulation of mRNA decay in the cytoplasm is crucial for controlling the abundance of cellular transcripts and the levels of protein expression, so regulation of long non-coding RNA decay in the nucleus is considered to be important for biological function. Although enzymatic pathways involved in cytoplasmic mRNA decay have been studied extensively, far less is known about those in nuclear long ncRNA decay. Here, we have investigated decay of metastasis associated lung adenocarcinoma transcript 1 (MALAT-1), which is a long (similar to 8 kb) ncRNA that is misregulated in many human cancers and was shown to be retained specifically in the nucleus in nuclear speckles, as a model of nuclear long ncRNA in mammalian cells. We have found that the half-life of MALAT-1 ranges from similar to 9 h to > 12 h in various cancer cells. Moreover, Xrn2, PM/Scl-75, PARN, and Mtr4, known nuclear RNases or RNA helicases, did not affect MALAT-1 degradation or single knockdown of these components did not change the MALAT-1 decay rate.