Rainbow trout hspb1 (hsp27): identification of two mRNA splice variants that show predominant expression in muscle tissues.

Here, I investigate features of the heat-shock protein beta1 (HspB1) that may be unique to cold-water fish. cDNAs encoding HspB1 were cloned from the rainbow trout Oncorhynchus mykiss, and two splice variants, Hspb1_tv1 and Hspb1_tv2, were identified. The C-terminus of the deduced proteins had a polyglutamic acid (polyE) stretch that is not found in other vertebrate HspB1s. In fish exposed to a continuous heat shock, the mRNA level of Hspb1_tv1 increased whereas that of b1_tv2 decreased. Northern blot and RT-PCR analyses showed that under normal physiological conditions Hspb1_tv1 mRNA is predominantly expressed in muscle tissues, although it is present in all organs. In contrast, Hspb1_tv2 mRNA is selectively expressed in muscle tissues, particularly in the heart. Distinctive features of rainbow trout Hspb1, such as having two splice variants and a polyE stretch, may contribute to the function of the protein under the typical low-temperature habitat of cold-water fish.