Translation May Be Regulated by Antisense RNA

Messenger RNA is transcribed using only one DNA strand as the template. This is referred to variously as the template strand, non-coding strand or antisense strand. The mRNA produced is consequently sense RNA. The other strand of DNA (the coding strand or sense strand) is not normally used as a template for transcription. If RNA were transcribed using the coding strand as template we would produce an RNA molecule complementary in sequence to the mRNA. This is known as antisense RNA and can base pair with its complementary mRNA, just as the two strands of DNA in the original gene base pair with each other (Fig. 11.08). [Note that uracil pairs with adenine in duplex RNA].

Antisense RNA is occasionally used in gene regulation both by bacteria and eukaryotes. If antisense RNA is made, it will base pair with the mRNA and prevent antisense RNA An RNA molecule that is complementary to mRNA

sense RNA Normal RNA that has been produced from the non-coding strand of DNA

Translation May Be Regulated by Antisense RNA 289

FIGURE 11.07 The Conformation of Translational Activator cPABP Responds to Light Intensity

Light initiates a chain reaction in photosystem II (PS II) and I (PS I) of plant chloroplasts whereby an electron transfer takes place through the electron transport chain. The electron reduces the disulfide bond of cPABP so changing its conformation and allowing it to bind mRNA and activate translation.

Photosystem I ®

Photosystem II

Binding site

fiOf. ill

lis.

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