Table 1. Composition and function of eukaryotic Lsm and Sm complexes.

Complexes		RNA partners	Cellular functions	Assembly
Sm	Sm Complex	U1, U2, U4 and U5 snRNAs3	mRNA splicing	Requires RNA103 In vertebrates, Sm complex association with snRNAs is chaperoned by SMN14
		U11, U12 and U4atac snRNAs104	mRNA splicing by the minor spliceosome105
		TLC1 (S.cerevisiae) TER1 (S.pombe)	Biogenesis and stability of telomerase RNA subunit106,107
	SmB, SmB’, SmD	hTR scaRNAs	Associate with telomerase RNA and scaRNAs in human cells, but role is unclear108	Unknown but the Sm complex chaperone SMN is also associated with telomerase109
Sm/Lsm	U7 Sm/Lsm complex	U7 snRNA	Essential for 3′ processing of histone mRNAs Lsm11 interacts with FLASH to recruit cleavage factors95	Requires SMN complex for assembly8
Lsm	Lsm2–8 complex	U6 snRNA	Stabilizes U6 snRNA and chaperone its interactions with U4, the pre-mRNA and Prp24/p11013,27,99	Spontaneous assembly in the absence of RNA110
		TER1 RNA (S.pombe)	Promotes association of telomerase catalytic subunit and protects the 3′ end of mature TER1 RNA from exonucleases107
	Lsm1–7 complex	Oligoadenylated cytoplasmic mRNAs	Prevents 3′ end trimming by exonucleases39 Recruits the decapping machinery40
		Oligouridylated histone mRNAs (in vertebrates)	Recruits the decapping machinery and Eri1 exonuclease to initiate degradation57,59,60
	Lsm2–7 complex	snR528 pre-RNase P20	Biological role is not clear
	Lsm2–4/6–8 complex	U8 snoRNA29	Biological role is not clear