Many promoter regions in genes transcribed by eukaryotic rna polymerase ii do not contain a tata box sequence. however, all three eukaryotic polymerases require tbp for transcription initiation regardless of the presence of a tata box in the promoter region. what hypothesis might explain why tbp is necessary for transcription from tata-less promoters
a. the dna-bending function of tbp cannot be performed by another protein in the general transcription factor complex.
b. tbp is still required for initial recognition of promoter sequences. this protein has an equal affinity for dna sequences with and without a tata box.
c. tbp is required for stabilizing the complex as it assembles on the promoter.
d. tbp is required for the catalytic activity of the rna polymerase.