Isolation and characterization of a cDNA encoding a putative high mobility group (HMG)--box protein from stored mRNA in resting cysts of the ciliate Oxytricha (Sterkiella) nova: ciliate macronuclear gene encoding a putative HMG-box protein.

We have isolated an cDNA after applying a DDRT-PCR analysis on mRNA from mature resting cysts of the ciliate Oxytricha (Sterkiella) nova. From this cDNA fragment the complete macronuclear minichromosome was obtained by using the Mac-End-PCR method. After cloning and sequencing, this cDNA shown certain similarity to HMG-like proteins. The analysis of the inferred amino acid sequence shown that this putative HMG-like protein has one HMG-box interrupted by a intron. The analysis of others characteristics (including a 3D model) confirms that it is a HMGB family protein. It is the first time that a macronuclear gene encoding a putative HMG-box protein is isolated from resting cysts of a stichotrich ciliate. The possible implications of this stored mRNA in the ciliate cryptobiotic stage are discussed.