Characterisation and quantification of earthworm cyclophilins: identification of invariant and heavy metal responsive isoforms

We report the identification of two earthworm cyclophilin genes, which rese mble the cytosolic cyclophilin-A and the signal sequence containing cycloph ilin-B. Using fully quantitative PCR we were able to assess the transcript regulation of both cyclophilin isoforms, as well as a further independent c ontrol gene (actin), during exposure to heavy metals. Whilst the expression of cyclophilin-B and actin remained exceptionally constant, cyclophilin-A was up-regulated 38-fold. This intriguing observation has profound implicat ions regarding cyclophilin's use as an invariant control and highlights the fact that it is essential to treat cyclophilin isoforms as separate entiti es, rather than one functional unit. (C) 1999 Elsevier Science B.V. All rig hts reserved.