Environmental reprogramming of the expression of protein kinase CK2 beta subunit in fish

The dramatic segregation of the nucleolar components in winter-acclimatized carp is the most striking cellular-phenotypical feature observed during th e seasonal adaptation of this fish toward the circannual changes in its hab itat. Our studies also show that the carp habitat temperature and photoperi od winter conditions provoke a remarkable reduction of both rRNA transcript ion and the processing of their precursors. To gain knowledge on the mechan isms involved in the regulation of nucleolar activity during the seasonal a daptation process, we studied the behavior of some genes, specifically snoR NA U3 and protein kinase CK2. Consistent with the reduction in the synthesis and processing of pre-rRNA o bserved during the cold season, the level of CK2 beta expression decreases in winter when compared to that attained in summer. Similarly, in winter, l iver and kidney cells contain lower levels of CK2 beta subunit protein comp ared to summer. CK2 is associated with or modifies different factors and en zymes involved in the nucleolar activity; therefore, its higher or lower co ntent could be part of the molecular mechanisms underlying the nucleolar se asonal changes that occur during the compensatory acclimatization process.