Endogenous Oligonucleotides of Human Milk and Their Possible Biological Function

Yu. Ya. Kit^1*, E. V. Kuligina¹, A. M. Onishchenko², L. V. Yurchenko¹, I. V. Romannikova¹, V. A. Richter¹, and V. V. Vlassov¹

¹Novosibirsk Institute of Bioorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, pr. Lavrent'eva 8, Novosibirsk, 630090 Russia; fax: (3832) 33-3677; E-mail: kit@niboch.nsc.ru

²Novosibirsk Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, pr. Lavrent'eva 10, Novosibirsk, 630090 Russia

^* To whom correspondence should be addressed.

Received October 26, 1998

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Oligonucleotides (ON) 4 to 60 nucleotides in length were isolated by ion-exchange chromatography on a column with Fractogel TSK DEAE-650 (M) from human milk which was hydrolyzed with proteinase K. ON from 60 to 16 nucleotides were degraded by RNase A but were resistant to DNase I, and, thus, they were ribooligonucleotides. In the presence of [gamma-³²P]ATP, ON and heparin inhibited the phosphorylation of 38- and 20-kD milk proteins and failed to affect the phosphorylation of a 76-kD protein. Human milk is believed to contain polyanion-dependent and polyanion-independent protein kinases. The influence of the ON on the activity of the cytotoxic fraction of human milk alpha-lactalbumin towards human mammary gland carcinoma MCF-7 cells was studied. The ON inhibited the cytostatic and cytotoxic effects of alpha-lactalbumin. Synthetic oligonucleotides and heparin had similar effects. The endogenous ON are suggested to be involved in the regulation of cytotoxic activity of human milk.

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KEY WORDS: human milk, oligonucleotides, alpha-lactalbumin, phosphorylation, apoptosis

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