Question

1. Transcriptional regulation in eukaryotes is controlled by both cis- and trans-acting elements. The following structure was isolated from honey bees. It shows such elements as well as parts of a gene body indicated with relative positions. The arrow denotes the transcription start site (the drawing is not in scale).

Figure 1

A) Indicate what the elements or segments, number 1, 2, 3 and 4, are most likely to stand for.

B) Which numbered segments can interact with trans-acting factors?

C) Which numbered segments are cis-acting elements?

Answer 1

Question-1 Indicate what the elements or segments, number 1, 2, 3 and 4, are most likely to stand for.

Segment -1: it represents the coding sequence of a gene --> exon;

Segment-2: It is transcription factor, which predominantly a trans-acting element and it is a eukaryotic TATA binding protein to promote transcription.

Segment-3: It is a promoter of eukaryotic TATA-box of DNA

Segment -4: It is an upstream enhancer element and possibly cis-acting element acceptable

Question-2: Which numbered segments can interact with trans-acting factors?

In the given figure, it has clearly observed that “4” ---> enhancers; number 3 ----> promoters. These segments interact with trans-regulatory factors.

Question-3: Which numbered segments are cis-acting elements?

In the figure, it has clearly observed that the 3 and 4 numbered segments are cis-acting elements.

Explanation:

The regulation of gene expression in eukaryotic cell:

The following are the three important areas of sites of transcription regulation.

1). Restricted access of polymerase to the gene: This is the regulation of transcription initiation, which is the most common target of regulatory mechanisms. This also includes the altering functions of histone remodelling enzymes, transcription factors, repressor proteins, enhancer proteins, etc.

2). Elongation of the RNA transcript: After the binding of polymerase to promoter region, it needs a set of factors to escape from the promoter and success transcription.

3). Termination of polymerase activity: The fate of RNA transcript is regulated by the number of factors that regulate the termination phase.

2). Splicing regulation (spliceosomes): pre- mRNA editing regulation: 5' capping, 3' poly adenylation, splicing are 3 crucial processes to edit the gene. It is illustrated that by inducing changes inside these genes, we can control further mRNA gene expression.

3). Controlling genes for expression genes to synthesise, tRNA, rRNA              

Transcription initiation is the most common target of regulatory mechanisms. The mechanisms include cis acting DNA binding elements that regulate gene expression. These are including enhancers and promoters associated with TATA box, initiators, response elements these cis-acting regulatory elements binds with transcription factors (trans-acting regulatory elements) to promote transcription. Normally trans acting elements are going to promote transcription by binding to TATA box.