Hsp are important family of proteins that buffer mutations, protect proteins against stresses and missfolding. Hsp let the organism to accumulate new mutations over the time without permitting to transcribe them. They are abundant in normal temperatures but highly induced by stress. Hsp, under certain conditions, interact with highly selected unstable proteins like kinases and transcription factors and signal transduction. Any mutation in these proteins leads to remarkable alteration in the developmental pathways.
However variation in nature indicates mutations’ occurrence!
Hsp could not protect against mutations until one of two circumstances occur; the concentration of mutations is high and if environment conditions change rapidly.
Studies found out that Hsp have a limited capacity to hold mutations but after that mutations would be expressed in the organism. Mutations also develop in fruit flies when exposed to high and low temperatures even with a normal HSP90 gene. So the hidden mutations in the flies turn up in harsh conditions to change fly’s proteins and phenotype.
Alternatively, some masked mutations and multiple polymorphisms become independent of Hsp if enriched by selection. The continuous selection of these traits would lead to continuous variation of them even thought if Hsp are functioning. This situation brings some cryptic questions about the limits of Hsp and what types of mutations they buffer and do Hsp accumulate then release mutations or just buffer them? Were Hsp absent in certain times then revealed? How efficient are they? Can they buffer all mutations or just selected types of them?
One probable answer might be certain; these proteins played important role in evolution history and need to be more investigated.
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References:
Pennisi, E 1998. ‘Heat Shock Protein Mutes Genetic Changes’, Science, New Series, Vol. 282, No. 5395, p. 1796.
Suzanne, Rutherford & Lindquist 1998. ‘Hsp90 as a capacitor for morphological evolution’, Nature, Vol. 396, No 6709, p.336-342.
Queitsch, Sangster & Lindquist 2002. ‘Hsp90 as a capacitor of phenotypic variation’, Nature 417, No. 6889, p. 618-624.
