Enhancerless GFP reporter constructs used in research conducted in mice contain a generic mouse gene promoter (TATA box) followed by a transcription start site and then a GFP gene cDNA. When such enhancerless reporter gene constructs are integrated into random locations in the mouse genome, about 10% of the time, high levels of tissue-specific GFP expression are detected, even though the reporter gene construct itself has no enhancer. How is this possible

the reporter gene can randomly insert near to an enhancer sequence which can induce its expression

Explanation

Enhancers are genetic sequences capable of activating gene expression by binding to specific proteins (e.g., transcription factors). Enhancers can regulate the expression of nearby genes located thousands of nucleotides away, i.e., over several kilobases away. In the human genome, it is well known that enhancers are scattered across the 98% of the genome. In this case, it is expected that the reporter GFP gene construct is randomly inserted near an enhancer sequence (a 10% chance of insertion), thereby being regulated by that enhancer.

micro/nanoscale topography surface exhibits many prominent properties and is extensively employed in biomedical device, microfluidic device and energy device fabrication. additionally, the clinical applications of biomaterials can be largely expanded with of nanostructured surfaces.

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.