Non-coding RNAs in human disease by Esteller
Types of ncRNAs and their functions
lnc RNAs are ncRNAs longer than 200 nt. ncRNAs include miRNAs, piRNAs, snoRNAs, lncRNAs (eg HOTAIR).
Small ncRNAs 22 nt. In animals mediate PTGS. Control translation of mRNA into proteins.
piRNAs are ncRNAs 24-30 nt in length. They are Dicer-independent and bind PIWI subfamily of Argonatute proteins involved in maintaining stability of genome in germline cells. Transcrobed from transpoable elements and other repetitive elements. Complex formed by piRANs and PIWI proteins suppressed TE expression and mobilisation. The mechanisms include cleaving TE transcripts by IWI proteins. This is mediated through base pairing recognition by piRNA. The 2nd is heterochromatin mediated gene silencing. PIWI class protiens PIWIL1 PIWIL2 and PIWIL4 are involved in ping pong amplification cycle. This creates antisense piRNAs that can repress trasncript of origin. PIWI proteins are linked to DNA methylation.