Table 8.

Human DNA helicases. nd, Not determined.

S. No.	Name of helicase	Mol. mass (kDa)	Nucleotide cofactors	Polarity	Remarks
1.	HDH I a	65	ATP, dATP	3′−5′	Can also unwind DNA/RNA and RNA/RNA hybrids; may be involved in rDNA transcription.
2.	HDH II/	87	ATP, dATP	3′−5′	Functions in dsDNA break repair and V(D)J recombination; regulator of DNA‐dependent
	Ku b	72			protein kinase
3.	HDH III c	46	ATP, dATP	3′−5′	Prefers replication fork‐like structure of substrates
4.	HDH IV d	100	ATP, dATP	5′−3′	Can unwind DNA/RNA hybrids
5.	HDH V e	92	ATP, dATP	3′−5′	Has highest turnover rate
6.	HDH VI f	128	ATP, dATP	3′−5′	Prefers replication fork‐like structure of substrates
7.	HDH VII g	36	nd	nd	Trimer of one molecule of hnRNP A1 and two molecules of annexin II
8.	HDH VIII h (G3GP)	68	ATP	5′−3′	A DNA and RNA helicase corresponding to G3 bp protein, an element of the RAS transduction  pathway, similar to E. coli RecBCD
9.	HDH IX g (RNP DO)	45	nd	nd	A Gly‐Arg rich protein identified as ribonuclear protein DO
10.	XPD/ERCC2 i	87	ATP, dATP	5′−3′	Functions in nucleotide excision repair; component of BTF2‐TFIIH transcription factor.
11.	XPB/ ERCC3 j	89	ATP	3′−5′	Functions in nucleotide excision repair; component of BTF2‐TFIIH transcription factor.
12.	Helicase ε k	72	ATP, dATP,  CTP	3′−5′	Helicase activity is dependent on HRP‐A
13.	Helicase µ l	110	ATP, dATP,	3′−5′	Stimulated by 5′‐tailed fork and SSB.
		90	CTP, dCTP
14.	RIP 100 m	100	ATP, dATP	3′−5′	Associated with RIP60; RIP60 binds to replication origin region of DHFR h
15.	Helicase Q1 n	73	ATP, dATP	3′−5′	Gene homologous to E. coli RecQ gene; identical to human DNA helicase I
16.	Helicase Q2 o	100	ATP	5′−3′	Identical with DNA helicase IV
17.	HchlR1 p	112	ATP	5′−3′	Can unwind RNA/DNA substrates. Unlike others it can translocate along ssDNA in both directions when substrate have a very long ssDNA region.
18.	HHcsA q	116	ATP, dATP	5′−3′	Hexameric protein.
19.	WRN helicase r	163	ATP, dATP ≫  DCTP, CTP	3′−5′	Mutated in Werner syndrome, homologous to RecQ and contains 3′‐5′ exonuclease activity
20.	BLM helicase s	≈ 160	ATP	3′−5′	Mutated in cells of Bloom's syndrome patient and belongs to RecQ family.
21.	Mcm4/6/7 complex t	≈ 600	ATP, dATP	3′−5′	The DNA unwinding activity is stimulated by SSB and forked DNA structures; can function as a replication helicase.
22.	HEL308 u	124.5	ATP, dATP	3′−5′	Homologous to DNA crosslink sensitivity protein Mus308 of D. melanogaster. Stimulated by RPA.
23.	HFDH1 v	≈ 120	ATP	3′−5′	First F‐box protein that possesses enzyme activity.
24.	Human RECQ1 w	75	ATP	3′−5′	Needs 3′ tail of 10 nt on the substrate to open the duplex; can unwinds blunt end substrate with bubble of 25 nt; stimulated by hRPA.
25.	BACH1 x	130	ATP	5′−3′	A nuclear phosphoprotein interacts with tumor suppressor, BRCA1. Involved in DSB repair and contain tumor suppression activity.

^a [63]; ^b [113]; ^c [5]; ^d [5]; ^e [ 5]; ^f [5]; ^g A. Falaschi & A. Ochem, unpublished data; ^h [114]; ⁱ [115]; ^j [116]; ^k [117]; ^l [118]; ^m [119]; ⁿ [120]; ^o [120]; ^p [121]; ^q [122]; ^r [123]; ^s [124]; ^t [37]; ^u [125]; ^v [126]; ^w [51]; ^x [127].