Question

I discovered a new long non-coding RNA that is transcribed in the antisense direction over an intron-exon junction of the gene. The intron from which the antisense RNA starts transcription has an IRE site. What affects does this lncRNA have on protein coded by this gene?

Answer 1

Answer-

The new long non-coding RNA that you have discovered is actually a 5' UTR ( 5' Untranslated Region ) site of an mRNA. The presence of the IRE site ( Iron Response Element ) at the intron from which antisense RNA starts transcription, actually proves it because this site (IRE) only locates at the 5' UTR site of a mRNA. This particular mRNA codes for ferritin protein.

The long non-coding RNA ( 5' UTR ) shows an important effect in Ferritin protein synthesis due to presence of that IRE site. Ferritin is an intracellular protein which stores iron and releases it in a controlled manner. The ferritin level is regulated in response to the iron supply.

IRE element is actually a special recognition sequence which can form stem-loop structure.When concentration of iron is low , an Iron Regulatory Protein (IRP) binds to the IRE .As because the UTR is now blocked due to this binding, small subunit of ribosome will unable to sit here & translation will not be initiated (preventing the synthesis of ferritin).On the other hand, when concentration of iron is high , free iron molecules bind with the Iron Regulatory Protein (IRP) .As a result, IRP is unable to bind to IRE & now ferritin will be synthesized as translation of that particular mRNA is occuring.(small subunit of ribosome is now able to sit at the 5' UTR & translation initiates).

In this way, this long non-coding RNA ( 5' UTR ) is affecting the synthesis of protein,ferritin, coded by that particular gene.