Polyadenylic acid polymerase activity in normal and leukemic human leukocytes

Area of Science:

• Biochemistry
• Molecular Biology
• Hematology

Background:

• Polyadenylic acid [poly(A)] polymerase plays a crucial role in RNA processing.
• Alterations in poly(A) polymerase activity have been implicated in various cancers, including leukemia.

Purpose of the Study:

• To investigate and compare the levels of soluble polyadenylic acid [poly(A)] polymerase and poly(A) nucleases in normal human blood lymphocytes and different types of leukemic blood cell populations.
• To determine if differences in poly(A) polymerase activity between acute and chronic leukemias are attributable to variations in poly(A)-degrading enzymes.

Main Methods:

• Quantification of soluble poly(A) polymerase and poly(A) nucleases in blood lymphocytes from normal individuals and leukemia patients.
• Enzyme activity assays and statistical analysis to compare enzyme levels between different groups.
• Fractionation of crude extracts using Sephadex G-75 to identify molecular forms of poly(A) polymerase.

Main Results:

• Significantly higher mean poly(A) polymerase activity was observed in acute leukemias (acute myeloblastic, monoblastic, lymphoblastic) compared to chronic lymphocytic leukemias and normal lymphocytes.
• A statistically significant difference (p < 0.01) was found between the poly(A) polymerase levels in chronic and acute leukemias.
• Differences in poly(A) polymerase levels between acute lymphoblastic leukemia and chronic lymphocytic leukemia persisted after fractionation and were not explained by variations in poly(A) nuclease activity.
• Fractionation revealed two distinct molecular forms of poly(A) polymerase activity in leukemic cell extracts.

Conclusions:

• Poly(A) polymerase activity is significantly elevated in acute leukemias compared to chronic leukemias.
• The observed differences in poly(A) polymerase levels are intrinsic to the polymerase enzyme and not due to alterations in poly(A) degrading enzymes.
• The presence of two molecular forms of poly(A) polymerase in leukemic cells warrants further investigation into their specific roles.