Transcription from the SV40 early‐early and late‐early overlapping promoters in the absence of DNA replication

Transcription for a hybrid SV40 promoter‐beta globin coding sequence recombinant initiates from both early‐early (EE) and late‐early (LE) SV40 start sites (EES and LES) in the absence of DNA replication. The 72‐bp repeat is essential to potentiate the elements of the two overlapping EE and LE promoters (EEP and LEP). Two current models, which can account for the EE to LE shift in RNA chain initiation during the SV40 replication cycle, are that LE transcription is linked to replication and occurs on newly replicated DNA molecules or that there are two promoter elements, a stronger EEP and a weaker LEP, T antigen repressing the EEP late in infection. Our results support the second model. A 5′‐TATTTAT‐3′ to 5′‐TATCGAT‐3′ mutation in the putative SV40 TATA box decreases transcription from EES, increases transcription from LES, and inhibits DNA replication. Therefore, this element acts as a classical TATA box for transcription, and yet is also important for DNA replication.