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Proteolytic Cleavage Activates the Mitochondrial Isoform of TOP3A

ABSTRACT: The TOP3A gene encodes two isoforms, one targeted to the nucleus and one to mitochondria. Nuclear TOP3A functions as part of the BTRR complex to resolve double Holliday junctions during homologous recombination, while the mitochondrial isoform separates hemicatenated daughter mitochondrial DNA molecules following DNA replication. Here, we show that the mitochondrial isoform of TOP3A undergoes proteolytic cleavage by the mitochondrial processing peptidase (MPP), removing ~90 amino acids from the C-terminus. This cleavage enhances the enzyme’s biochemical properties, increasing single-stranded DNA binding and decatenation activity. Notably, all BTRR complex subunits except TOP3A are absent from mitochondria, suggesting that proteolytic processing enables TOP3A to function autonomously in mtDNA maintenance. We propose that this cleavage represents a post-import maturation step that tailors TOP3A to its mitochondrial context by uncoupling it from nuclear protein interactions and enhancing its catalytic efficiency.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Proteomics Core Facility

LAB HEAD: Claes M. Gustafsson

PROVIDER: PXD064926 | Pride | 2025-10-01

REPOSITORIES: Pride

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			Action	DRS
	3164_sample1_CtermTr_TMT_semiTrypsin_QEHF_190506_40_63.msfView	Msf
	3164_sample1_CtermTr_TMT_semiTrypsin_QEHF_190506_40_63.pdResult	Other
	4754_DoNotMerge_S1toS8_Lumos_231023_19to42.pdResult	Other
	4860_peptideA_10ppm_Xcorr3_iSTD15ug_withalkylation_QE.pdResultView	Other
	4860_peptideB_10ppm_Xcorr3_iSTD15ug_withalkylation_QE.pdResultView	Other

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