This study investigates the presence and distribution of methylated nucleosides in messenger RNA (mRNA) from Novikoff hepatoma cells. The researchers used poly(A) tract analysis to study methylation in mRNA obtained from these cells. RNA containing a poly(A) segment was isolated from polysomal RNA using oligo(dT)-cellulose chromatography. Sucrose density gradient centrifugation confirmed the RNA as mRNA. Enzymatic degradation of the RNA to nucleosides was followed by DEAE-cellulose (borate) chromatography, which separated 2'-O-methylnucleosides from base-methylated nucleosides. Approximately 50% of the radioactivity was recovered in each fraction. High-speed liquid chromatography of the 2'-O-methylnucleoside fraction revealed four peaks corresponding to the four 2'-O-methylnucleoside standards. The base-methylnucleoside fraction showed a unique pattern, with ribosomal RNA and tRNA having complex base-methylated nucleoside patterns, while mRNA was predominantly composed of N-methyladenosine. These results indicate a unique distribution of methylated nucleosides in mRNA. The study also found that methylation is essential for proper rRNA processing, as methylation of 45S RNA does not occur in the absence of methionine, and mature ribosomal RNA is not formed. The presence of methylnucleosides in mRNA may reflect a cellular mechanism for the selective processing of certain mRNA sequences. The study further shows that mRNA methylation is less than rRNA methylation, as a percentage of total nucleotides. The base-methylation pattern in mRNA is distinct from that of rRNA or tRNA, with mRNA primarily containing N6-methyladenosine and/or 1-methyladenosine. The results suggest that methylation plays an essential role in mRNA processing and may be involved in the regulation of gene expression. The study also indicates that the presence of a poly(A) tract in mRNA may be related to the base modification in this segment. The findings highlight the importance of post-transcriptional modification in the synthesis of eukaryotic RNA and the potential role of methylation in the regulation of genetic expression.This study investigates the presence and distribution of methylated nucleosides in messenger RNA (mRNA) from Novikoff hepatoma cells. The researchers used poly(A) tract analysis to study methylation in mRNA obtained from these cells. RNA containing a poly(A) segment was isolated from polysomal RNA using oligo(dT)-cellulose chromatography. Sucrose density gradient centrifugation confirmed the RNA as mRNA. Enzymatic degradation of the RNA to nucleosides was followed by DEAE-cellulose (borate) chromatography, which separated 2'-O-methylnucleosides from base-methylated nucleosides. Approximately 50% of the radioactivity was recovered in each fraction. High-speed liquid chromatography of the 2'-O-methylnucleoside fraction revealed four peaks corresponding to the four 2'-O-methylnucleoside standards. The base-methylnucleoside fraction showed a unique pattern, with ribosomal RNA and tRNA having complex base-methylated nucleoside patterns, while mRNA was predominantly composed of N-methyladenosine. These results indicate a unique distribution of methylated nucleosides in mRNA. The study also found that methylation is essential for proper rRNA processing, as methylation of 45S RNA does not occur in the absence of methionine, and mature ribosomal RNA is not formed. The presence of methylnucleosides in mRNA may reflect a cellular mechanism for the selective processing of certain mRNA sequences. The study further shows that mRNA methylation is less than rRNA methylation, as a percentage of total nucleotides. The base-methylation pattern in mRNA is distinct from that of rRNA or tRNA, with mRNA primarily containing N6-methyladenosine and/or 1-methyladenosine. The results suggest that methylation plays an essential role in mRNA processing and may be involved in the regulation of gene expression. The study also indicates that the presence of a poly(A) tract in mRNA may be related to the base modification in this segment. The findings highlight the importance of post-transcriptional modification in the synthesis of eukaryotic RNA and the potential role of methylation in the regulation of genetic expression.