ALTERATION OF PFK SUBUNIT PROTEIN, SYNTHESIS, AND MESSENGER-RNA DURING NEONATAL BRAIN-DEVELOPMENT

During neonatal maturation of rat brain, a similar biphasic relationsh ip exists between the previously reported pattern of glucose utilizati on and levels of each type of 6-phosphofructo-1-kinase (PFK) subunit p rotein, relative synthesis, and mRNA. The increasing amounts of each s ubunit isoform generally correlated with elevated protein synthesis wh ich was promoted by greater amounts of each type of subunit mRNA. For each parameter, the early phase, 1 to 10 days after birth, was charact erized by small increases, and the subsequent period from ten to thirt y days postpartum was characterized by a much greater rate of increase . By 30 days after birth, adult values were observed. The apparent eff iciency of translation of each type of PFK subunit mRNA in brain sugge sts that the M-type subunit mRNA is the most efficient and that the L- type subunit mRNA is the least. The greatest relative increases in sub unit protein, mRNA, and synthesis were observed for the C-type subunit . Since enhanced translation apparently makes little, if any, contribu tion, a possible explanation of these phenomena could be increased tra nscription of the PFK genes. These neonatal changes could involve age- dependent alteration of methylation of the PFK gene promotor(s) and/or activity of effecters of the transcription of the PFK genes.