Structural Analysis of MALAT1 long non-coding RNA in cells and in evolution.

Abstract

Although not canonically polyadenylated, the long non-coding RNA MALAT1 (Metastasis Associated Lung Adenocarcinoma Transcript 1) is stabilized by a highly conserved 76 nucleotide triple helix structure on its 3' end. The entire MALAT1 transcript is over 8,000 nucleotides long in humans. The strongest structural conservation signal in MALAT1 (as measured by co-variation of base-pairs) is in the triple helix structure. Primary sequence analysis of co-variation alone does not reveal the degree of structural conservation of the entire full-length transcript, however. Furthermore, RNA structure is often context dependent; RNA binding proteins that are differentially expressed in different cell types may alter structure. We investigate here the in cell and cell free structures of the full-length human and green monkey (Chlorocebus sabaeus) MALAT1 transcripts in multiple tissue-derived cell lines using SHAPE chemical probing. Our data reveal levels of uniform structural conservation in different cell lines, in cells and cell free, and even between species, despite significant differences in primary sequence. The uniformity of the structural conservation across the entire transcript suggests that, despite seeing co-variation signals only in the triple helix junction of the lncRNA, the rest of the transcript's structure is remarkably conserved at least in primates and across multiple cell types and conditions.