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Overview

Uniprot ID	Q9ULC4
Protein Name	Malignant T-cell-amplified sequence 1
Gene Name	MCTS1
Organism	Homo sapiens

Kla Sites from experimental identification

Position	Flanking peptide
23	QLKTSVIKGIKNQLI
51	MPKKDPVKIVRCHEH

Function

Translation regulator forming a complex with DENR to promote translation reinitiation. Translation reinitiation is the process where the small ribosomal subunit remains attached to the mRNA following termination of translation of a regulatory upstream ORF (uORF), and resume scanning on the same mRNA molecule to initiate translation of a downstream ORF, usually the main ORF (mORF). The MCTS1/DENR complex is pivotal to two linked mechanisms essential for translation reinitiation. Firstly, the dissociation of deacylated tRNAs from post-termination 40S ribosomal complexes during ribosome recycling. Secondly, the recruitment in an EIF2-independent manner of aminoacylated initiator tRNA to P site of 40S ribosomes for a new round of translation (PubMed:16982740, PubMed:20713520, PubMed:37875108). This regulatory mechanism governs the translation of more than 150 genes which translation reinitiation is MCTS1/DENR complex-dependent (PubMed:16982740, PubMed:20713520, PubMed:37875108). Consequently, modulates various unrelated biological processes including cell cycle regulation and DNA damage signaling and repair (PubMed:10440924, PubMed:11709712, PubMed:12637315, PubMed:15897892, PubMed:16322206, PubMed:17016429, PubMed:17416211, PubMed:9766643). Notably, it positively regulates interferon gamma immunity to mycobacteria by enhancing the translation of JAK2 (PubMed:37875108)

Protein Sequence

10 MFKKFDEKEN 20 VSNCIQLKTS 30 VIKGIKNQLI 40 EQFPGIEPWL 50 NQIMPKKDPV 60 KIVRCHEHIE 70 ILTVNGELLF 80 FRQREGPFYP 90 TLRLLHKYPF 100 ILPHQQVDKG 110 AIKFVLSGAN 120 IMCPGLTSPG 130 AKLYPAAVDT 140 IVAIMAEGKQ 150 HALCVGVMKM 160 SAEDIEKVNK 170 GIGIENIHYL 180 NDGLWHMKTY K

Gene Ontology

Classification	GO ID	Description
Cellular Component	GO:0005737	cytoplasm
Cellular Component	GO:0005829	cytosol
Molecular Function	GO:0043024	ribosomal small subunit binding
Molecular Function	GO:0000339	RNA cap binding
Molecular Function	GO:0003743	translation initiation factor activity
Biological Process	GO:0006974	DNA damage response
Biological Process	GO:0006351	DNA-templated transcription
Biological Process	GO:0001731	formation of translation preinitiation complex
Biological Process	GO:0075522	IRES-dependent viral translational initiation
Biological Process	GO:0032790	ribosome disassembly
Biological Process	GO:0002188	translation reinitiation

Reference

[1] He J, Lai T, Zhou Z, Yang H, Lei Z et al.. Multiomics profiling reveals the involvement of protein lactylation in nonhomologous end joining pathway conferring radioresistance in lung adenocarcinoma cell.. Sci Rep 15(1):24651. 2025 Jul 9. PMID: 40634431.

[2] Wu Q, Li Z, Gong T, Zheng X, Zhou X et al.. Porphyromonas gingivalis infection induces lysine lactylation reprogramming in human umbilical vein endothelial cells.. Front Cell Infect Microbiol 16:1706727. 2026. PMID: 41696360.