Suppose that a single protein is significantly overexpressed in one of two different cell lines. The proteins are identical, but
Northern blot analysis indicates that the mRNA for the protein in the overexpressing cell line is about 200 base pairs shorter. Subsequent reverse transcriptase PCR has revealed that the truncation occurs in the 3ʹ untranslated region. How might this lead to overexpression of the protein?
Many mRNAs have sequences of 50 - 150 nt rich in A and U in the 3' untranslated region. These sequences, called AU-rich elements, are important to regulate mRNA stability, because they bind proteins that target the mRNA for degradation.
When a protein binds to the AU-rich element of the mRNA, the polyA tail can be shortened and/or the 5'cap is removed, promoting mRNA degradation. In addition, the AU-rich elements in some mRNAs have been shown to inhibit protein translation.
The mRNA of the overexpressing cell line is about 200nt shorter than the normal cell line; this could mean that it has a deletion in the 3'UTR comprising an AU-rich element. If this is missing, the mRNA will have an extended half-life (because it won't be targeted for degradation) or it will be translated more. As a result, the protein expression will be increased.
All living things contain carbon so an argument could be made that carbon was the basis. Or it could be oxygen because all living things in one way require oxygen to live, even plants and fish who pull oxygen from the water molecules.
Enzymes are organic substances that are produced to catalyse and speed up chemical reactions in chemical reactions. Enzymes take part in product formation. They lower the activation energy by acting as catalysts during a chemical reaction thus products are formed faster.
Usually the denser oceanic plate is subsided by the less dense continental plate. As the oceanic plate dives into the mantle, it begins to melt and the part of liquid rock begin to rises through the fissures created due to stress in the convergent boundary. The magma then erupts, through these fissures, into volcanic mountains along the boundary.
