J. Biol. Chem., Vol. 265, Issue 14, 7927-7932, 05, 1990
Structure and function of the promoter of the carrot V-type H(+)-ATPase catalytic subunit gene
I Struve, T Rausch, P Bernasconi and L Taiz
Department of Biology, Sinsheimer Laboratories, University of California, Santa Cruz 95064.
We investigated the 5'-upstream region of the gene encoding the catalytic
subunit of the V-type H(+)-ATPase in Daucus carota. A genomic sublibrary
was screened with a cDNA probe, and a 4-kilobase genomic clone was obtained
covering the first two exons and about 3 kilobases of the 5'-upstream
sequence. The intron/exon boundaries matched established consensus
sequences. Within 240 base pairs (bp) upstream of the initiation codon
three putative TATA boxes were found. Ribonuclease protection and primer
extension analysis indicated that the three TATA boxes corresponded to two
major and one minor transcription start sites. The flanking sequences of
the two more proximal TATA boxes were nearly identical. Additional sequence
motifs with putative regulatory function are two CCAAT boxes, an
Sp1-binding consensus sequence, and long (TATA)n stretches within 800 bp of
the 5'-upstream sequence. Transcriptional fusions to the beta-glucuronidase
reporter gene were made for two different promoter constructs, and the
resulting plasmids were mobilized into Agrobacterium tumefaciens. The
analysis of beta- glucuronidase activities in the transformed carrot calli
showed that 240 bp of the upstream sequence, including all three TATA
boxes, led to low but detectable beta-glucuronidase expression; however,
the larger construct, which included the putative Sp1-binding sequence and
the (TATA)n stretches, led to an approximately 6-fold higher beta-
glucuronidase expression. Histochemical analysis of beta-glucuronidase
activity in the transformed calli showed no preferential expression in any
specific cell type, in keeping with the presumed "housekeeping" character
of the V-type H(+)-ATPase catalytic subunit gene.