Human skeletal-muscle cells were infected with increasing concentrations of adenovirus expressing SREBP1a or SREBP1c (Ad-SREBP1a or Ad-SREBP1c) as indicated in the Materials and methods section. Total cell lysates were prepared, 24 h after infection, and analysed for the presence of precursor and mature forms of SREBP-1 and for INSIG-1 using specific antibodies (A). α-Tubulin is shown as a loading control. In parallel, total RNA was prepared from muscle cells overexpressing the SREBP-1 isoforms (24 h after adenofection) and analysed for the expression of SREBP-1a and SREBP-1c transcripts using RT–qPCR (B). Due to sequence identities between the endogenous gene and the adenoviruses, SREBP-1c transcripts were measured when SREBP-1a adenovirus was used and, conversely, SREBP-1a mRNA was determined when SREBP-1c mature protein was overexpressed. Results are presented as means±S.E.M. (n=3). *P<0.05.