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Professor and Interim Director Center for Molecular Medicine and Genetics Wayne State University School of Medicine Room 3238 Scott Hall Ph.D., Yeshiva (Albert Einstein College
of Medicine), 1971
Research areas:
Current lab members:
Communication:
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Research:
We study the molecular genetics of cytochrome c oxidase, the protein complex that catalyzes the terminal step in the electron transport chain, the transfer of an electron from cytochrome c to oxygen. The mammalian thirteen-subunit holoenzyme contains ten subunits encoded in the nucleus and three in mitochondria. Of the ten nuclear subunits, three are present as isoforms in most species, a contractile muscle-specific form (H isoform) and a form present ubiquitously (L form). We are studying the expression, function and evolution of selected nuclear genes, with emphasis on the two isoform genes for subunit VIIa that we isolated. These isoforms are developmentally regulated such that the L form is present initially in fetal heart and muscle but switches during development to the adult H form.
Promoter function: We have been studying promoter function of several isoform genes to understand whether and how COX subunit transcription is coordinately controlled, and whether it is responsive to energetics. For the L formof subunit VIIa (COX7AL), we showed that a 92-bp basal promoter promotes most of the activity of this gene and contains sites for the nuclear respiratory factors NRF-1 and NRF-2, which contribute to the transcription of a number of nuclear genes involved in mitochondrial respiratory activity, and also at least four Sp1 motifs. We have also isolated the subunit VIIa heart/muscle isoform gene (COX7AH) from several species. The human gene is myotube-specific when expressed in myogenic (C2C12) cells. Expression depends on the single Mef2 site and/or the most distal of three E-boxes. Furthermore, we have isolated the mouse gene, which was previously thought to be lacking in rodents. Our studies thus far show little relation between transcriptional regulation of COX7AL and COX7AH.
For COX7C, which is ubiquitously expressed, we have isolated the gene and shown that 167 bp of DNA surrounding the transcriptional start site contains its minimal promoter. This basal promoter contains two functional YY1 sites and at least one site for NRF-2. Mutation of both YY1 sites eliminates most of the promoter activity. Mutation at the upstream YY1 site significantly reduces the efficiency of transcript initiation at the major start site and thus plays the dominant role in COX7C regulation. COX7C is, thus, the second nuclear gene of COX that is regulated by YY1, suggesting that it is a third common factor, along with NRF-1 and NRF-2, to be associated with COX gene regulation.
Molecular evolution: We have examined three individual subunits thus far.
The COX4 gene, which we originally showed in 1992 to evolve rapidly in human (Proc. Natl. Acad. Sci. USA 89, 5266-5270), was analyzed in more detail (Wu et al., below) in the two groups of anthropoid primates, the catarrhines (hominoids, cercopithecoids) and platyrrhines (ceboids), as well as one prosimian primate (lorisiform). Phylogenetic analysis of COX4 sequence data revealed that accelerated nonsynonymous substitution rates were evident in the early evolution of both catarrhines and, to a lesser extent, platyrrhines. These accelerated rates were followed later by decelerated rates, suggesting that positive selection for adaptive amino acid replacement became purifying selection, preserving replacements that had occurred. The evidence for positive selection was especially pronounced along the catarrhine lineage to hominoids in which the nonsynonymous rate was first faster than the synonymous rate, then later much slower.
We examined relative evolutionary rates for the COX6A heart (H) and liver (L) isoform genes along the length of the molecule, specifically in relation to potential tissue-specific function(s) of the two isoforms. The COX6AH gene evolved more rapidly than the ubiquitously-expressed COX6AL gene, for both nonsynonymous (amino acid changes) and synonymous (silent) substitutions. In addition, comparisons among orthologous COX6A isoforms revealed that amino acid sequences are more conserved in the mitochondrial matrix end than elsewhere. Maximum parsimony analysis revealed that after the ancestral COX6A gene duplicated to yield the genes for the H and L isoforms, the sequences encoding the mitochondrial matrix region of the COX VIa protein initially experienced an elevated rate of nonsynonymous substitutions and then later a decelerated rate relative to synonymous substitutions. This pattern is expected for positive selection of adaptive amino acid replacements followed by purifying selection to preserve the replacements.
COX7AH also shows an accelerated nonsynonymous substitution rate, which occurred between the origin of primates and the divergence of Old World monkeys and Apes. Rate accelerations have been noted for at least three other COX-related genes in this time period, suggesting that the COX holoenzyme has experienced an episode of adaptive evolution. A third member of the gene family, COX7ARP (SIG81), has recently been described. Phylogenetic analysis of COX7ARP suggests that it is a product of gene duplication prior to the divergence of COX7AH and COX7AL. Although its function is currently unknown, low N/S ratios in mammalian evolution suggest that COX7ARP is of functional importance. Examination of nucleotide substitution rates of four domains of the COX7A isoforms identified the mitochondrial targeting residues as potentially having tissue-specific importance. This region of the COX7A genes apparently experienced an accelerated nonsynonymous substitution rate after gene duplication, but has been relatively conserved in mammalian evolution, consistent with the evolution of tissue-specific function. Finally, ongoing examination of the replacement rate for other subunits suggests that co-evolution among subunits is taking place.
Recent Publications:
W. Wu, M. Goodman, M.I. Lomax and L.I. Grossman (1997). Molecular evolution of cytochrome c oxidase subunit IV: evidence for positive selection in simian primates. J. Mol. Evol. 44, 477-491.
L.I. Grossman and M.I. Lomax (1997). Invited review: Nuclear genes for cytochrome c oxidase. Biochim. Biophys. Acta1352, 174-192.
R.S. Seelan and L.I. Grossman (1997). Structural organization and promoter analysis of the bovine cytochrome c oxidase subunit VIIc gene: A functional role for YY1. J. Biol. Chem. 272, 10175-10181.
T. Schmidt, S.A. Jaradat, M. Goodman, M.I. Lomax and L.I. Grossman (1997). Molecular evolution of mammalian cytochrome c oxidase: rate variation between subunit VIa isoforms. Mol. Biol. Evol.44, 477-491.
L.I. Grossman, R.S. Seelan and S.A. Jaradat (1998). Transcriptional regulation of mammalian cytochrome coxidase genes. Electrophoresis19, 1254-1259.
S.A. Jaradat, M.S.H. Ko, and L.I. Grossman (1998). Tissue specific expression and mapping of the COX7AHgene in mouse. Genomics49, 363-370.
N.J. Bachman, W. Wu, L.I. Grossman and M.I. Lomax (1999). COX4, the gene for cytochrome c oxidase subunit IV, and NOC4, a closely linked gene, are controlled by a bidirectional promoter. Mamm. Genome10, 506-512.
T.R. Schmidt, M. Goodman and L.I. Grossman (1999). Molecular evolution of the COX7A gene family in primates. Mol. Biol. Evol. 16, 619-626.
M. Hüttemann, N. Mühlenbein, T.R. Schmidt, L.I. Grossman and B. Kadenbach (2000). Isolation and sequence of the human cytochrome c oxidase subunit VIIaL gene. Biochim. Biophys. Acta 1492, 252-258.
W. Wu, T.R. Schmidt, M. Goodman and L.I. Grossman (2000). Molecular evolution of cytochrome c oxidase subunit I in primates: Is there co-evolution between mitochondrial and nuclear genomes? Mol. Phylogenet Evol. 17, 294-304.
B.C. White, J.M. Sullivan, D.J. DeGracia, B.J. O'Neil, R.W. Newmar, L.I. Grossman, J.A. Rafols and G.S. Krause (2000). Global brain ischemia and reperfusion: Molecular mechanisms of neuronal injury. J. Neurol. Sci. 179, 1-33.
E.H. McConkey and A. Varki. Cosignatories: Allman, J, Benirschke, K, Crick, F, Deacon, TW, de Waal, F, Dugaiczyk, A, Gagneux, P, Goodman, M, Grossman, LI, Gumucio, D, Insel, T, Kidd, KK, King, M-C, Krauter, K, Kucherlapati, R, Motulsky, AG, Nelson, D, Oefner, P, Palade, G, Ruvolo, M, Ryder, OA, Sikela, J, Stewart, C-B, Stone, A & Woodruff, D. (2000). A primate genome project deserves high priority. Science 289: 1295-6.
L.I. Grossman, T.R. Schmidt, D. Wildman and M. Goodman (2001). Molecular evolution of aerobic energy metabolsim in primates. Mol. Phylogenet Evol. 18, 26-36.
T.R. Schmidt, W. Wu, M. Goodman and L.I. Grossman (2001). The evolution of nuclear and mitochondrial encoded subunit interaction in cytochrome c oxidase. Mol. Biol. Evol, in press.
M. Hüttemann, B. Kadenbach and L.I. Grossman (2001). Mammalian subunit IV isoforms of cytochrome c oxidase. Gene, in press.