Slipped-strand mispairing within a polycytidine tract in transcriptional regulator mga leads to M protein phase variation and Mga length polymorphism in Group A Streptococcus
The M protein, a major virulence factor of Group A Streptococcus (GAS), is regulated by the multigene regulator Mga. An unexplained phenomena frequently occurring with in vitro genetic manipulation or culturing of M1T1 GAS strains is the loss of M protein production. This study was aimed at elucidat...
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Frontiers Media S.A.
2023-06-01
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| Series: | Frontiers in Microbiology |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fmicb.2023.1212149/full |
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| author | Benfang Lei Tracey S. Hanks Yunjuan Bao Mengyao Liu |
| author_facet | Benfang Lei Tracey S. Hanks Yunjuan Bao Mengyao Liu |
| author_sort | Benfang Lei |
| collection | DOAJ |
| description | The M protein, a major virulence factor of Group A Streptococcus (GAS), is regulated by the multigene regulator Mga. An unexplained phenomena frequently occurring with in vitro genetic manipulation or culturing of M1T1 GAS strains is the loss of M protein production. This study was aimed at elucidating the basis for the loss of M protein production. The majority of M protein-negative (M−) variants had one C deletion at a tract of 8 cytidines starting at base 1,571 of the M1 mga gene, which is designated as c.1571C[8]. The C deletion led to a c.1571C[7] mga variant that has an open reading frame shift and encodes a Mga-M protein fusion protein. Transformation with a plasmid containing wild-type mga restored the production of the M protein in the c.1571C[7] mga variant. Isolates producing M protein (M+) were recovered following growth of the c.1571C[7] M protein-negative variant subcutaneously in mice. The majority of the recovered isolates with reestablished M protein production had reverted back from c.1571C[7] to c.1571C[8] tract and some M+ isolates lost another C in the c.1571C[7] tract, leading to a c.1571C[6] variant that encodes a functional Mga with 13 extra amino acid residues at the C-terminus compared with wild-type Mga. The nonfunctional c.1571C[7] and functional c.1571C[6] variants are present in M1, M12, M14, and M23 strains in NCBI genome databases, and a G-to-A nonsense mutation at base 1,657 of M12 c.1574C[7] mga leads to a functional c.1574C[7]/1657A mga variant and is common in clinical M12 isolates. The numbers of the C repeats in this polycytidine tract and the polymorphism at base 1,657 lead to polymorphism in the size of Mga among clinical isolates. These findings demonstrate the slipped-strand mispairing within the c.1574C[8] tract of mga as a reversible switch controlling M protein production phase variation in multiple GAS common M types. |
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| language | English |
| last_indexed | 2024-03-13T03:14:09Z |
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| spelling | doaj.art-912ef860dd954de59bd431f274b3646e2023-06-26T05:24:32ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2023-06-011410.3389/fmicb.2023.12121491212149Slipped-strand mispairing within a polycytidine tract in transcriptional regulator mga leads to M protein phase variation and Mga length polymorphism in Group A StreptococcusBenfang Lei0Tracey S. Hanks1Yunjuan Bao2Mengyao Liu3Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, United StatesDepartment of Microbiology and Cell Biology, Montana State University, Bozeman, MT, United StatesState Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei, ChinaDepartment of Microbiology and Cell Biology, Montana State University, Bozeman, MT, United StatesThe M protein, a major virulence factor of Group A Streptococcus (GAS), is regulated by the multigene regulator Mga. An unexplained phenomena frequently occurring with in vitro genetic manipulation or culturing of M1T1 GAS strains is the loss of M protein production. This study was aimed at elucidating the basis for the loss of M protein production. The majority of M protein-negative (M−) variants had one C deletion at a tract of 8 cytidines starting at base 1,571 of the M1 mga gene, which is designated as c.1571C[8]. The C deletion led to a c.1571C[7] mga variant that has an open reading frame shift and encodes a Mga-M protein fusion protein. Transformation with a plasmid containing wild-type mga restored the production of the M protein in the c.1571C[7] mga variant. Isolates producing M protein (M+) were recovered following growth of the c.1571C[7] M protein-negative variant subcutaneously in mice. The majority of the recovered isolates with reestablished M protein production had reverted back from c.1571C[7] to c.1571C[8] tract and some M+ isolates lost another C in the c.1571C[7] tract, leading to a c.1571C[6] variant that encodes a functional Mga with 13 extra amino acid residues at the C-terminus compared with wild-type Mga. The nonfunctional c.1571C[7] and functional c.1571C[6] variants are present in M1, M12, M14, and M23 strains in NCBI genome databases, and a G-to-A nonsense mutation at base 1,657 of M12 c.1574C[7] mga leads to a functional c.1574C[7]/1657A mga variant and is common in clinical M12 isolates. The numbers of the C repeats in this polycytidine tract and the polymorphism at base 1,657 lead to polymorphism in the size of Mga among clinical isolates. These findings demonstrate the slipped-strand mispairing within the c.1574C[8] tract of mga as a reversible switch controlling M protein production phase variation in multiple GAS common M types.https://www.frontiersin.org/articles/10.3389/fmicb.2023.1212149/fullGroup A StreptococcusStreptococcus pyogenesM proteinMgaphase variationslipped-strand mispairing |
| spellingShingle | Benfang Lei Tracey S. Hanks Yunjuan Bao Mengyao Liu Slipped-strand mispairing within a polycytidine tract in transcriptional regulator mga leads to M protein phase variation and Mga length polymorphism in Group A Streptococcus Frontiers in Microbiology Group A Streptococcus Streptococcus pyogenes M protein Mga phase variation slipped-strand mispairing |
| title | Slipped-strand mispairing within a polycytidine tract in transcriptional regulator mga leads to M protein phase variation and Mga length polymorphism in Group A Streptococcus |
| title_full | Slipped-strand mispairing within a polycytidine tract in transcriptional regulator mga leads to M protein phase variation and Mga length polymorphism in Group A Streptococcus |
| title_fullStr | Slipped-strand mispairing within a polycytidine tract in transcriptional regulator mga leads to M protein phase variation and Mga length polymorphism in Group A Streptococcus |
| title_full_unstemmed | Slipped-strand mispairing within a polycytidine tract in transcriptional regulator mga leads to M protein phase variation and Mga length polymorphism in Group A Streptococcus |
| title_short | Slipped-strand mispairing within a polycytidine tract in transcriptional regulator mga leads to M protein phase variation and Mga length polymorphism in Group A Streptococcus |
| title_sort | slipped strand mispairing within a polycytidine tract in transcriptional regulator mga leads to m protein phase variation and mga length polymorphism in group a streptococcus |
| topic | Group A Streptococcus Streptococcus pyogenes M protein Mga phase variation slipped-strand mispairing |
| url | https://www.frontiersin.org/articles/10.3389/fmicb.2023.1212149/full |
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