The octamer motif ATGCAAAT is recognized indistinguishably by two mammalian transcription factors: one that is expressed ubiquitously and referred to here as Oct-l, and another, Oct-2, that is expressed in lymphoid cells. We report the cDNA cloning of the human oct-1 gene, which encodes Oct-l, by screening kgtl 1 recombinant phage in situ for octamer motif-specific DNA binding. Transcriptional regulation depends largely on the sequence-specific interaction of trans-activator proteins with cis-acting promoter elements. Sequence-specific trans-activators contain two essential domains for function: a DNA-binding domain and a trans-activation domain. As first shown by fusion of the bacterial lexA DNA-binding domain to the yeast GAL4 trans-activation domain (Brent and Ptashne 1985), these domains can be interchanged. The specificity of transcriptional activation is conferred by the DNA-binding domain, which targets the trans-activator to the promoter carrying a corresponding DNA-binding site(s) (for review, see Ptashne 1988). To date, trans-activation domains have displayed little promoter specificity. For example, the yeast GAL4 trans-activator can stimulate a variety of promoters in mammalian cells provided that GAL4

From these data we conclude that vitamin D was significantly associated with muscle power and force in adolescent girls.

Whereas the genes coding for trimethyl guanosine‐capped snRNAs are transcribed by RNA polymerase II, the U6 RNA genes are transcribed by RNA polymerase III. In this study, we have analyzed the cis‐regulatory elements involved in the transcription of a mouse U6 snRNA gene in vitro and in frog oocytes. Transcriptional analysis of mutant U6 gene constructs showed that, unlike most known cases of polymerase III transcription, intragenic sequences except the initiation nucleotide are dispensable for efficient and accurate transcription of U6 gene in vitro. Transcription of 5′ deletion mutants in vitro and in frog oocytes showed that the upstream region, within 79 bp from the initiation nucleotide, contains elements necessary for U6 gene transcription. Transcription studies were carried out in frog oocytes with U6 genes containing 5′ distal sequence; these studies revealed that the distal element acts as an orientation‐dependent enhancer when present upstream to the gene, while it is orientation‐independent but distance‐dependent enhancer when placed down‐stream to the U6 gene. Analysis of 3′ deletion mutants showed that the transcription termination of U6 RNA is dependent on a T cluster present on the 3′ end of the gene, thus providing further support to other lines of evidence that U6 genes are transcribed by RNA polymerase III. These observations suggest the involvement of a composite of components of RNA polymerase II and III transcription machineries in the transcription of U6 genes by RNA polymerase III.

Despite improvements in 25(OH)D status, treatment with vitamin D(2) was not shown to increase mineral accretion, bone geometry or strength, muscle force, or power. There were greater increases in jump velocity in girls with the lowest baseline 25(OH)D concentrations. Lack of effect of intervention after the period of peak mineral and muscle mass accretion suggests that earlier action is required.

In eukaryotes, activation of transcription involves an interplay between activators bound to cis-regulatory elements and factors bound to basal elements near the start site of transcription. The basal elements, for example the TATA box or proximal sequence element (PSE) of small nuclear RNA (snRNA) promoters, nucleate the assembly of basal transcription complexes, components of which interact with activators. Although one basal transcription complex can interact with many activators, it is unclear whether different basal transcription complexes can direct different responses to particular activators. We show here that changing the arrangement of basal elements can alter the response to transcriptional activation domains. Indeed, in the human U6 snRNA promoter, point mutation of either a TATA box or PSE results in diametrically opposed responses to VP16- and Sp1-derived activation domains. These basal elements can even discriminate small changes in an activation domain. Thus the arrangement of basal promoter elements provides a mechanism for differential regulation of transcription.