Int J Biochem Mol Biol 2013;4(4):179-190
Original Article
Modulation of formation of the 3’-end of the human argininosuccinate synthetase mRNA
by GT-repeat polymorphism
Shih-Heng Tseng, Cheng-Yi Cheng, Miao-Zeng Huang, Ming-Yi Chung, Tsung-Sheng Su
Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan; Department of Medical
Research, Taipei Veterans General Hospital, Taipei, Taiwan
Received October 21, 2013; Accepted November 26, 2013; Epub December 15, 2013; Published December 30, 2013
Abstract: Microsatellites are abundant in the human genome and may acquire context-dependent functions. A highly polymorphic GT
microsatellite is located downstream of the poly(A) signal of the human argininosuccinate synthetase (ASS1) gene. The ASS1 participates in
urea and nitric oxide production and is a rate-limiting enzyme in arginine biosynthesis. To examine possible involvement of the GT
microsatellite in ASS1 mRNA 3’-end formation, ASS1 minigene constructs were used in transient transfection for assessment of poly(A) site
usage by S1 nuclease mapping. Synthesis of the major human ASS1 mRNA is found to be controlled by two consecutive non-canonical poly(A)
signals, UAUAAA and AUUAAA, located 7 nucleotides apart where a U-rich sequence and the GU microsatellite serve as their respective
downstream GU/U-rich elements. Moreover, AUUAAA utilization is affected by the GU-repeat number possibly leading to differential regulation
of ASS1 polyadenylation in individuals with different repeat numbers. Interestingly, the less efficient UAUAAA motif is noted to be the major
ASS1 poly(A) signal possibly as a result of an indispensable downstream U-rich element and restricted utilization of the AUUAAA motif by the
presence of extended GU-repeats. The UAUAAA motif and the GT microsatellite are conserved only in primates whereas AUUAAA motif is
present in all mammals analyzed. The suboptimal UAUAAA motif and the utilization of the polymorphic GT microsatellite as polyadenylation
signal of the ASS1 gene may be used as a strategy in primates to modulate ASS1 level in response to interactions of genetic and
environmental factors. (IJBMB1310001).
Keywords: Argininosuccinate synthetase 1 (ASS1), GT-repeat polymorphism, microsatellite, polyadenylation signal, poly(A) downstream
element, gene regulation
Address correspondence to: Dr. Ming-Yi Chung, Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan 112. Tel:
+886-2-2871-2121 x3265; Fax: +886-2-2875-1562; E-mail: mychung@vghtpe.gov.tw; Dr. Tsung-Sheng Su, Department of Life Sciences and
Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan 112. Tel: +886-2-2826-7000 x5131; Fax: +886-2-2820-2449; E-
mail: su31659@gmail.com
Original Article
Modulation of formation of the 3’-end of the human argininosuccinate synthetase mRNA
by GT-repeat polymorphism
Shih-Heng Tseng, Cheng-Yi Cheng, Miao-Zeng Huang, Ming-Yi Chung, Tsung-Sheng Su
Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan; Department of Medical
Research, Taipei Veterans General Hospital, Taipei, Taiwan
Received October 21, 2013; Accepted November 26, 2013; Epub December 15, 2013; Published December 30, 2013
Abstract: Microsatellites are abundant in the human genome and may acquire context-dependent functions. A highly polymorphic GT
microsatellite is located downstream of the poly(A) signal of the human argininosuccinate synthetase (ASS1) gene. The ASS1 participates in
urea and nitric oxide production and is a rate-limiting enzyme in arginine biosynthesis. To examine possible involvement of the GT
microsatellite in ASS1 mRNA 3’-end formation, ASS1 minigene constructs were used in transient transfection for assessment of poly(A) site
usage by S1 nuclease mapping. Synthesis of the major human ASS1 mRNA is found to be controlled by two consecutive non-canonical poly(A)
signals, UAUAAA and AUUAAA, located 7 nucleotides apart where a U-rich sequence and the GU microsatellite serve as their respective
downstream GU/U-rich elements. Moreover, AUUAAA utilization is affected by the GU-repeat number possibly leading to differential regulation
of ASS1 polyadenylation in individuals with different repeat numbers. Interestingly, the less efficient UAUAAA motif is noted to be the major
ASS1 poly(A) signal possibly as a result of an indispensable downstream U-rich element and restricted utilization of the AUUAAA motif by the
presence of extended GU-repeats. The UAUAAA motif and the GT microsatellite are conserved only in primates whereas AUUAAA motif is
present in all mammals analyzed. The suboptimal UAUAAA motif and the utilization of the polymorphic GT microsatellite as polyadenylation
signal of the ASS1 gene may be used as a strategy in primates to modulate ASS1 level in response to interactions of genetic and
environmental factors. (IJBMB1310001).
Keywords: Argininosuccinate synthetase 1 (ASS1), GT-repeat polymorphism, microsatellite, polyadenylation signal, poly(A) downstream
element, gene regulation
Address correspondence to: Dr. Ming-Yi Chung, Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan 112. Tel:
+886-2-2871-2121 x3265; Fax: +886-2-2875-1562; E-mail: mychung@vghtpe.gov.tw; Dr. Tsung-Sheng Su, Department of Life Sciences and
Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan 112. Tel: +886-2-2826-7000 x5131; Fax: +886-2-2820-2449; E-
mail: su31659@gmail.com
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