A dispersed repetitive element named ingi, which is present in the genome of the protozoan parasite Trypanosoma brucei, is described. One complete 5.2-kilobase element and the ends of two others were sequenced. There were no direct or inverted terminal repeats. Rather, the ends consisted of two halves of a previously described 512-base-pair transposable element (G. Hasan, M. J. Turner, and J. S. Cordingley, Cell 37:333-341, 1984). Oligo(dA) tails and possible insertion site duplications suggested that ingi is a retroposon.The sequenced element appears to be a pseudogene copy of an original retroposon with one or more open reading frames occupying most of its length. Significant homologies of the encoded amino acid sequences with reverse transcriptases and mammalian long interpersed nuclear element sequences suggest a remote evolutionary origin for this kind of retroposon.

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Theileria parva is an obligate, intracellular, parasitic protozoan that causes East Coast fever, an acute leukemia‐like disease of cattle. T. parva and the related parasite, Theileria annulata, are unique among protozoa in that their intralymphocytic stages induce transformation of bovid lymphocytes. Comparison of in vitro protein kinase activities between uninfected IL‐2‐dependent T lymphoblasts and T. parva‐infected lymphocytes revealed a 4.7‐ to 12‐fold increase in total phosphorylation and the induction of a group of Theileria infection‐specific phosphoproteins. The enzyme that phosphorylates these substrates is a serine/threonine kinase with substrate and effector specificities of casein kinase (CK) II. Northern blot analyses revealed a 3.9‐ to 6.0‐fold increase in CKII alpha mRNA in the infected cells relative to the controls. Furthermore, a marked increase of CKII antigen was observed on Western blots of materials prepared from the infected cell lines. The antibovine CKII antibody used in these studies immunoprecipitated a protein kinase that phosphorylated casein in a reaction that was inhibited by low (nM) quantities of heparin. Our data show marked increases of bovine CKII at the transcriptional, translational and functional levels in T. parva‐infected lymphocytes, relative to quiescent cells or IL‐2‐dependent parental lymphoblasts. Bovine CKII thus appears to be constitutively activated in these cells and we propose that this kinase may be an important element in the signal‐transducing pathways activated by Theileria in bovid lymphocytes and perhaps in some leukemic cells.