Limits...
Regulation of class switch recombination and somatic mutation by AID phosphorylation.

McBride KM, Gazumyan A, Woo EM, Schwickert TA, Chait BT, Nussenzweig MC - J. Exp. Med. (2008)

Bottom Line: Using a combination of mass spectrometry and immunochemical approaches, we found that in addition to S38, AID is also phosphorylated at position threonine 140 (T140).Mutation of either S38 or T140 to alanine does not impact catalytic activity, but interferes with class switching and somatic hypermutation in vivo.This effect is particularly pronounced in haploinsufficient mice where AID levels are limited.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10021, USA.

ABSTRACT
Activation-induced cytidine deaminase (AID) is a mutator enzyme that initiates somatic mutation and class switch recombination in B lymphocytes by introducing uracil:guanine mismatches into DNA. Repair pathways process these mismatches to produce point mutations in the Ig variable region or double-stranded DNA breaks in the switch region DNA. However, AID can also produce off-target DNA damage, including mutations in oncogenes. Therefore, stringent regulation of AID is required for maintaining genomic stability during maturation of the antibody response. It has been proposed that AID phosphorylation at serine 38 (S38) regulates its activity, but this has not been tested in vivo. Using a combination of mass spectrometry and immunochemical approaches, we found that in addition to S38, AID is also phosphorylated at position threonine 140 (T140). Mutation of either S38 or T140 to alanine does not impact catalytic activity, but interferes with class switching and somatic hypermutation in vivo. This effect is particularly pronounced in haploinsufficient mice where AID levels are limited. Although S38 is equally important for both processes, T140 phosphorylation preferentially affects somatic mutation, suggesting that posttranslational modification might contribute to the choice between hypermutation and class switching.

Show MeSH

Related in: MedlinePlus

Percentage of GC B cells from AIDS38A and AIDT140A mice. (A) Representative FACS analysis that shows percentage of FAS+GL7+ GC B cells in AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and wild-type (WT) mice 10 d after immunization. (B) Percentage of GC B cells in the lymph nodes of AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and WT mice 10 d after immunization from 6–8 mice. Each point represents an immunization experiment from a single mouse.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2571933&req=5

fig5: Percentage of GC B cells from AIDS38A and AIDT140A mice. (A) Representative FACS analysis that shows percentage of FAS+GL7+ GC B cells in AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and wild-type (WT) mice 10 d after immunization. (B) Percentage of GC B cells in the lymph nodes of AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and WT mice 10 d after immunization from 6–8 mice. Each point represents an immunization experiment from a single mouse.

Mentions: AID-deficient mice and humans have large GCs compared with controls (12, 14). To determine whether this effect is caused by loss of AID protein or its activity, we measured the number of GC B cells in AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and wild-type mice (Fig. 5, A and B). We found that the amount of AID activity was inversely proportional to the size of the GC response. AID−/− mice showed the highest number of GC B cells, wild-type mice the fewest, and AID+/− haploinsufficient mice were intermediate between the two (Fig. 5, A and B). Decreasing AID activity, but not protein, in AIDS38A/− mice resulted in an increase in the number of GC B cells proportional with the relative decrease in activity when compared with AID+/− controls (Fig. 5, A and B). We conclude that the number of GC B cells in immunized mice is inversely proportional to the amount of AID activity.


Regulation of class switch recombination and somatic mutation by AID phosphorylation.

McBride KM, Gazumyan A, Woo EM, Schwickert TA, Chait BT, Nussenzweig MC - J. Exp. Med. (2008)

Percentage of GC B cells from AIDS38A and AIDT140A mice. (A) Representative FACS analysis that shows percentage of FAS+GL7+ GC B cells in AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and wild-type (WT) mice 10 d after immunization. (B) Percentage of GC B cells in the lymph nodes of AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and WT mice 10 d after immunization from 6–8 mice. Each point represents an immunization experiment from a single mouse.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2571933&req=5

fig5: Percentage of GC B cells from AIDS38A and AIDT140A mice. (A) Representative FACS analysis that shows percentage of FAS+GL7+ GC B cells in AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and wild-type (WT) mice 10 d after immunization. (B) Percentage of GC B cells in the lymph nodes of AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and WT mice 10 d after immunization from 6–8 mice. Each point represents an immunization experiment from a single mouse.
Mentions: AID-deficient mice and humans have large GCs compared with controls (12, 14). To determine whether this effect is caused by loss of AID protein or its activity, we measured the number of GC B cells in AID−/−, AID+/−, AIDT140A/−, AIDS38A/−, and wild-type mice (Fig. 5, A and B). We found that the amount of AID activity was inversely proportional to the size of the GC response. AID−/− mice showed the highest number of GC B cells, wild-type mice the fewest, and AID+/− haploinsufficient mice were intermediate between the two (Fig. 5, A and B). Decreasing AID activity, but not protein, in AIDS38A/− mice resulted in an increase in the number of GC B cells proportional with the relative decrease in activity when compared with AID+/− controls (Fig. 5, A and B). We conclude that the number of GC B cells in immunized mice is inversely proportional to the amount of AID activity.

Bottom Line: Using a combination of mass spectrometry and immunochemical approaches, we found that in addition to S38, AID is also phosphorylated at position threonine 140 (T140).Mutation of either S38 or T140 to alanine does not impact catalytic activity, but interferes with class switching and somatic hypermutation in vivo.This effect is particularly pronounced in haploinsufficient mice where AID levels are limited.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10021, USA.

ABSTRACT
Activation-induced cytidine deaminase (AID) is a mutator enzyme that initiates somatic mutation and class switch recombination in B lymphocytes by introducing uracil:guanine mismatches into DNA. Repair pathways process these mismatches to produce point mutations in the Ig variable region or double-stranded DNA breaks in the switch region DNA. However, AID can also produce off-target DNA damage, including mutations in oncogenes. Therefore, stringent regulation of AID is required for maintaining genomic stability during maturation of the antibody response. It has been proposed that AID phosphorylation at serine 38 (S38) regulates its activity, but this has not been tested in vivo. Using a combination of mass spectrometry and immunochemical approaches, we found that in addition to S38, AID is also phosphorylated at position threonine 140 (T140). Mutation of either S38 or T140 to alanine does not impact catalytic activity, but interferes with class switching and somatic hypermutation in vivo. This effect is particularly pronounced in haploinsufficient mice where AID levels are limited. Although S38 is equally important for both processes, T140 phosphorylation preferentially affects somatic mutation, suggesting that posttranslational modification might contribute to the choice between hypermutation and class switching.

Show MeSH
Related in: MedlinePlus