The catalytic subunit of human DNA polymerase ϵ, an enzyme involved in nuclear DNA replication and repair, is encoded by thePOLE1 gene. This gene is composed of 51 exons spanning at least 97 kb of genomic DNA. It was found to encode three alternative mRNA splice variants that differ in their 5ʹ-terminal sequences and in the N-termini of the predicted proteins. A CpG island covers the promoter region for the major transcript in HeLa cells. This promoter is TATA-less and contains several putative binding sites for transcription factors typical of S-phase-up-regulated and serum-responsive promoters. Potential promoter regions were also identified for the two other alternative transcripts. Interestingly, no nuclear polyadenylation signal sequence was detected in the 3ʹ-untranslated region, although a poly(A) tail was present. These results suggest a complicated regulatory machinery for the expression of the humanPOLE1 gene, including three alternative transcripts expressed from three promoters.