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Open Access

The telomere-specific non-LTR retrotransposons SART1 and TRAS1 are suppressed by Piwi subfamily proteins in the silkworm, Bombyx mori

  • Tsuneyuki Tatsuke1, 2,
  • Kosuke Sakashita1,
  • Yuki Masaki1,
  • Jae Man Lee1,
  • Yutaka Kawaguchi1 and
  • Takahiro Kusakabe1Email author
Cellular & Molecular Biology LettersAn International Journal200915:118

Received: 9 April 2009

Accepted: 24 November 2009

Published: 27 November 2009


The telomere structures in Bombyx mori are thought to be maintained mainly by the transposition of the specialized telomeric retroelements SART and TRAS. The silkworm genome has telomeric TTAGG repeats and telomerase, but this telomerase displays little or no activity. Here, we report that the transcription of the telomeric retroelements SART1 and TRAS1 is suppressed by the silkworm Piwi subfamily proteins BmAgo3 and Siwi. The silkworm Piwi subfamily was found to be expressed predominantly in the gonads and early embryo, as in other model organisms, but in BmN4 cultured cells, these proteins formed granules that were separate from the nuage, which is a different behaviour pattern. The expression of TRAS1 was increased in BmN4 cells when BmAgo3 or Siwi were silenced by RNAi. Our results suggest that B. mori Piwi proteins are involved in regulating the transposition of telomeric retroelements, and that the functional piRNA pathway is conserved in BmN4 cultured cells.

Key words

Bombyx mori SART1TRAS1TelomerePiwi