Sense and antisense transcripts in the histone H1 ( HIS-1) locus of Leishmania major

• Published in: International journal for parasitology Vol. 33; no. 9; pp. 965 - 975
• Main Authors: Belli, Sabina I, Monnerat, Séverine, Schaff, Cédric, Masina, Slavica, Noll, Tanja, Myler, Peter J, Stuart, Kenneth, Fasel, Nicolas
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-08-2003; Elsevier Science
• Subjects: Animals; Antisense transcription; Biological and medical sciences; Blotting, Northern - methods; DNA, Antisense - analysis; DNA, Complementary - analysis; Fundamental and applied biological sciences. Psychology; Histone H1; Histones - genetics; Humans; Leishmania; Leishmania major; Leishmania major - genetics; Leishmaniasis, Cutaneous - transmission; Life cycle. Host-agent relationship. Pathogenesis; Polymerase Chain Reaction - methods; Protozoa; Transcription, Genetic; Virulence; Histone H1; Antisense transcription; Leishmania; Kinetoplastida; Protozoa; Host parasite relation; Protozoal disease; Life history; Transcription; Parasite; Antisense RNA; Parasitosis; Leishmaniasis; Gene expression; Infection; Locus; Leishmania major
• ISSN: 0020-7519; 1879-0135
• DOI: 10.1016/S0020-7519(03)00126-7

Histone H1 in the parasitic protozoan
Leishmania is a developmentally regulated protein encoded by two genes,
HIS-1.1 and
HIS-1.2. These genes are separated by ∼20 kb of sequence and are located on the same DNA strand of chromosome 27. When Northern blots of parasite RNA were probed with
HIS-1 strand-specific riboprobes, we detected sense and antisense transcripts that were polyadenylated and developmentally regulated. When the
HIS-1.2 coding region was replaced with the coding region of the neomycin phosphotransferase gene, antisense transcription of this gene was unaffected, indicating that the regulatory elements controlling antisense transcription were located outside of the
HIS-1.2 gene, and that transcription in
Leishmania can occur from both DNA strands even in the presence of transcription of a selectable marker in the complementary strand. A search for other antisense transcripts within the
HIS-1 locus identified an additional transcript (
SC-1) within the intervening
HIS-1 sequence, downstream of adenine and thymine-rich sequences. These results show that gene expression in
Leishmania is not only regulated polycistronically from the sense strand of genomic DNA, but that the complementary strand of DNA also contains sequences that could drive expression of open reading frames from the antisense strand of DNA. These findings suggest that the parasite has evolved in such a way as to maximise the transcription of its genome, a mechanism that might be important for it to maintain virulence.