Table 1.

The Y-family polymerases from the three domains of life and their key properties

Gene name	Protein name	Properties
Escherichia coli
dinB	Pol IV	• Creates –1 frameshifts when overexpressed in vivo
		• Bypasses N2-dG adducts efficiently and accurately
		• Involved in TLS of alkylation damage in vivo
umuD and umuC	Pol V	• Major TLS polymerase in E. coli; is able to traverse a vast array of lesions
		• Unique among Y-family polymerases in that it is comprised of a heterotrimer of UmuD′ (~24 kDa) and UmuC (~48 kDa) to form an ~72 kDa UmuD′2C complex
		• Interacts with RecA and ATP to form the highly active Pol V Mut polymerase
Sulfolobus solfataricus
dpo4	Dpo4	• Archaeal orthologue of E.coli Pol IV and human Pol κ
		• Multiple crystal structures of Dpo4 in the process of bypassing a variety of DNA lesions have been solved
Saccharomyces cerevisiae
REV1	Rev1	• Specifically incorporates dCMP opposite abasic sites, template G and a limited number of other, minor groove adducts
		• Interacts with the B-family TLS polymerase Pol ζ (which is comprised of Rev3 and Rev7) to stimulate Pol ζ-dependent TLS in vivo
RAD30	Pol η	• First Y-family polymerase to be shown to be a bona fide DNA polymerase
		• Can bypass a T-T CPD accurately and efficiently
Homo sapiens
REV1	REV1	• Like the yeast Rev1 protein, it specifically incorporates dCMP opposite dG and abasic sites
		• Acts as a scaffold protein that interacts with the Y-family polymerases Pol η, Pol ι and Pol κ, as well as the B-family TLS polymerase Pol ζ (which is comprised of Rev3 and Rev7)
		• Generates mutations at G-C base pairs during immunoglobulin gene somatic hypermutation
POLH (also known as XPV and RAD30A)	Pol η	• Bypasses a T-T CPD efficiently and with the same accuracy as undamaged DNA
		• Defects lead to XPV
		• Accumulates in replication foci
		• Is subject to ubiquitylation and phosphorylation
		• Generates mutations at A-T base pairs during immunoglobulin gene somatic hypermutation
POLI (also known as RAD30B)	Pol ι	• In human cells protein is 715 aa in length, but an additional in-frame 25 aa, conserved from frogs to humans, produces a 740 aa protein as a minor species (B. Coull and A.R.L., unpublished observations)
		• Has unique replication fidelity, replicating template dA reasonably accurately, but replicating template dT in a highly error-prone manner
		• Accumulates in replication foci, but resides in these foci for a shorter time than Pol η
POLK (also known as DINB1)	Pol κ	• Enzyme is prone to making –1 frameshift mutations, but can accurately and efficiently bypass a number of N2-dG lesions
		• Has additional roles in the repair synthesis step of nucleotide excision repair

aa, amino acid; CPD, cyclobutane pyrimidine dimer; Pol, DNA polymerase; TLS, translesion synthesis; XPV, variant form of xeroderma pigmentosum.