Wednesday, 7 January 2015

Is it time to review the Central Dogma??

Which biologist worth his or her salt doesn’t know it? It is the main stay of biology and genetics. It describes the basic structures of living organisms. To jog your memory I will revisit it. The central Dogma has been in existence for the longest time and is the main and central doctrine in biology and specifically genetics.  The term was first mentioned by Francis Crick in the 1950s. Principally, it states that deoxyribonucleic acid (DNA) has codes of bases that are transcribed into messenger RNA (mRNA) which is in turn translated into proteins that are part of tissues and organs in organisms.
The central Dogma has been the main stay in molecular biology for the many years. There have however been discoveries that over time have challenged the ‘linearity’ of the central dogma ie DNA-RNA-protein. The first formative discovery was the ‘reversed’ central dogma by the discovery of reverse transcriptase by David Baltimore in 1978. Reverse transcriptase was observed to use RNA as a template to make DNA. In the classical central dogma is unidirectional and so this observation goes against it and only considers it as an ‘exemption’.  

The second discovery was the observation that there exists non-coding RNA.  The central dogma indicates that translation yielding to proteins is the final step. However it does not envisage a case like that of non-coding RNAs which are in their self finality.  This goes against the central dogma.
The third and the most recent discovery is ‘reverse translation’. This has been established through the discovery that proteins (now called PRIONs) can be use in transferring information an observation that has never been thought of in the central dogma. Prions are essentially proteins that can propagate themselves and can as well be transmitted. They are known to cause disease by entering an organism and causing the conformation of existing proteins into their ‘disease conformation’. The fact that a protein affects the conformation of another protein goes against the central dogma.

The other discovery that dents the central dogma is the observation of the functioning of the ribosome quality control complex (RQC) of Saccharomyces cerevisiae. This complex plays a role in translation even in eukaryotes. If protein synthesis at the ribosomal stage goes wrong then this mechanism comes into play where the protein being translated to is destroyed. A twist was observed in RQC where proteinswithin this complex (rqc2p and Ltn1) were observed to initiate loading of alanine and threonine charged amino acids without the involvement of mRNA and ribosome. This shows that proteins can dictate formation of other proteins without involvement of mRNA. This violates the central dogma in a huge way.

The observations detailed above apart from reverse transcription which is detailed as an exemption of the central dogma indicate violations of the central dogma. Despite some of these observations being actively being researched on, there are still enough points that prove that the central dogma might have many more ‘exemptions’. It is only time that will tell how long proven discoveries will continue being treated as ‘exemptions’.

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