Noncoding RNAs and pancreatic cancer

Table 1 Main classes and function of human noncoding RNAs

RNA types	Length (nt)	Function
Small non-coding RNAs (< 200 nt)
Protein synthesis RNAs
Transfer RNAs	About 80	Carrying amino acids to connect with mRNA
Ribosomal 5S and 5.8S RNAs	121-200	Component of ribosomes
Small nucleolar RNAs	70-200	Involved in maturation of other non-coding RNAs
Small nuclear RNAs	About 150	Joining with proteins to form spliceosomes controlling alternative splicing
Regulatory RNAs
MicroRNAs	20-23	Negatively regulating gene expression by joining an enzyme and blocking mRNA, or speeding its breakdown
Small interfering RNAs	21-22	Silencing specific genes in a sequence-specific manner.
PIWI-interacting RNAs	About 25-33	Controlling retrotransposition and regulating methylation.
Promoter-associated short RNAs	< 200	Regulating gene expression through interaction with gene promoter sites
Long non-coding RNAs (> 200 nt)
Ribosomal 28S and 18S RNAs	200-5070	Component of ribosomes
Long intergenic non-coding RNAs or long intronic non-coding RNAs	> 200	Various
Telomere-associated ncRNAs	100 bp > 9 kb	Negative regulators of telomere
Antisense RNAs		Binding and blocking the translation of mRNA target
Promoter-associated short RNAs	> 200	Regulating gene expression through interaction with gene promoter sites
Transcribed-ultraconserved regions	200-799	Long-range enhancer-like activity, maintenance of splicing factor expression levels and transcription regulation