Neela wrote:Can someone translate this for engineers? I did read Abhijit"s translation and didnt get it.
I am an engineer too but will bravely attempt still to translate this. May not be entirely accurate.
A very novel therapeutic method is being attempted. This involves a process known as ‘gene silencing’.
The ultimate purpose of a gene in the DNA is to produce a protein through a two-stage process, transcription and translation. This is known as gene expression. Gene silencing is the technique to interrupt this gene expression. The DNA in the nucleus has the code for making a protein which is copied by the messenger RNA (mRNA) in a process known as transcription. This mRNA exits the nucleus into cytoplasm where copied instructions are used to synthesize the protein in the process known as translation. The cytoplasm (i.e. the portion outside the nucleus but still within the cell) contains basic ingredients that are needed to make these proteins. A virus, like coronavirus, injects its mRNA into the cell and makes copies of its protein, thereby causing infection. The idea in gene silencing is to stop this 'translation' process by targetting the mRNA and destroying it.
We have help at hand for this process within the DNA itself. Now, genes in the DNA have regions within themselves (known as intergenic areas) where there are certain types of micro RNAs (miRNA) which control or regulate the post-transcription process of gene expression, that is after transcription occurs in the nucleus but before translation occurs in cytoplasm. The miRNAs are non-coding RNA molecules (i.e. they cannot copy a gene to make a protein) which are very short in length. They interfere with the mRNA which carries the protein-making copy of the genetic code from the DNA (and therefore this process is known as RNAi or RNA interference).
In order to do this, the miRNA needs to get into cytoplasm and then act. The way it happens is as follows: the miRNA genes are transcribed in the nucleus by the same RNA polymerase enzyme leading to a hairpin-type miRNA (which means there are two strands, but not helical as in a DNA structure); this miRNA, known as pri-miRNA, or primary micro RNA, is further trimmed by other enzymes; the resulting trimmed transcript is known as a pre-miRNA, i.e., precursor miRNA; this is transported out of the nucleus.
In the cytoplasm, an enzyme called dicer removes the hairpin bend of the pre-miRNA making it into two strands, but still attached, that is a double-stranded micro RNA (ds miRNA) molecule. Later, these strands split, with one strand known as passenger miRNA being discarded. The other useful strand known as guide miRNA (or gRNA) attaches itself to a free-floating protein in the cytoplasm known as RISC (RNA Induced Silencing Complex). RISC uses the gRNA as a template for recognizing complementary mRNA. When it finds a complementary strand, it activates the RNase enzyme which cleaves the RNA into bits. This process which is important in gene regulation by microRNAs can be used in defense against viral infections because the virion carries only mRNA when it enters the cytoplasm of the cell. The trick is perhaps to find the correct gRNA that can latch on to the viral mRNA thus allowing RISC to destroy it.