Question

1. Briefly explain what will happen to the transcription of a gene, if its core promoter elements (Class II promoter with 3 elements: BRE, TATA and Inr) are moved downstream to the TSS (transcription site)?
2. Explain why eukaryotic cells have general and specific transcription factors?

Answer 1

In genetics a promoter is a sequence of DNA to which proteins bind that initiate transcription of a single RNA from the DNA downstream of it. This RNA may encode a protein, or can have a function in and of itself, such as tRNA, mRNA, or rRNA. Promoters are located near the transcription start sites of genes, upstream on the DNA. Promoters can be about 100-1000 base pairs long.

In molecular biology, a downstream promoter element is a core promoter element. Like all core promoters, the downstream promoter element plays an important role in the initiation of gene transcription by RNA polymerase ll.It is located about 28- 33 nucleotides downstream of the transcription start site.To begin transcriding a gene, RNA polymerase dinds to the DNA of the gene at a region called the promoter. Each gene has its own promoter. A promoter contains DNA sequences that let RNA polymerase or its helper proteins attach to the DNA.

Promoters are a vital component of expression vectors because they control the binding of RNA polymerase to DNA. RNA polymerase transcribes DNA to mRNA which is uitimately translated into a functional protein. Thus the promoter region controls when and where in the organism your gene of interest is expressed.

In eukaryotes an important class of transcription factors called general transcription factors(GTFs) are necessary for transcription to occur. Many of these GTFs do not actually bind DNA, but rather are part of the large transcription preinitiation complex that interacts with RNA polymerase directly.

GTFs first bind to the promoter, then start transcription. GTFs are also intimately involved in the process of gene regulation and most are required for life. Specific transcription factors act on individual genes, raather than all of them.