In yeast this protein participates in mitochondrial biogenesis and stress response [1,2]. And also seems that may affect the NAM7 function, possibly at the level of mRNA turnover [3].

1: MBR1 and MBR3, two related yeast genes that can suppress the growth defect of hap2, hap3 and hap4 mutants. Daignan-Fornier B, Nguyen CC, Reisdorf P, Lemeignan B, Bolotin-Fukuhara M; Mol Gen Genet. 1994;243:575-583. PMID:8208248

2: The MBR1 gene from Saccharomyces cerevisiae is activated by and required for growth under sub-optimal conditions. Reisdorf P, Boy-Marcotte E, Bolotin-Fukuhara M; Mol Gen Genet. 1997;255:400-409. PMID:9267436

3: Two adjacent nuclear genes, ISF1 and NAM7/UPF1, cooperatively participate in mitochondrial functions in Saccharomyces cerevisiae. Altamura N, Dujardin G, Groudinsky O, Slonimski PP; Mol Gen Genet. 1994;242:49-56. PMID:7506349