Spontaneous bleeding in a patient on enoxaparin with poor renal function.

Creatinine-based equations are used as standard ways to estimate glomerular filtration rate and kidney function. Unfortunately, serum creatinine varies based on factors such as age, gender, and muscle mass. Overestimation of renal function by creatinine-based equations can be dangerous for renally dosed medications, such as enoxaparin. We present a patient who developed spontaneous bleeding on enoxaparin where kidney function was significantly overestimated by creatinine-based equations. The use of cystatin C levels, which are creatinine independent, can provide a better prediction of renal function.

Herpes simplex virus-1 DNA primase: a remarkably inaccurate yet selective polymerase.

Herpes simplex virus-1 primase misincorporates the natural NTPs at frequencies of around one error per 30 NTPs polymerized, making it one of the least accurate polymerases known. We used a series of nucleotide analogues to further test the hypothesis that primase requires Watson-Crick hydrogen bond formation to efficiently polymerize a NTP. Primase could not generate base pairs containing a complete set of hydrogen bonds in an altered arrangement (isoguanine.isocytosine) and did not efficiently polymerize dNTPs completely incapable of forming Watson-Crick hydrogen bonds opposite templating bases incapable of forming Watson-Crick hydrogen bonds. Similarly, primase did not incorporate most NTPs containing hydrophobic bases incapable of Watson-Crick hydrogen bonding opposite natural template bases. However, 2-pyridone NTP and 4-methyl-2-pyridone NTP provided striking exceptions to this rule. The effects of removing single Watson-Crick hydrogen bonding groups from either the NTP or templating bases varied from almost no effect to completely blocking polymerization depending both on the parental base pair (G.C vs A.T/U) and which base pair of the growing primer (second, third, or fourth) was examined. Thus, primase does not absolutely need to form Watson-Crick hydrogen bonds to efficiently polymerize a NTP. Additionally, we found that herpes primase can misincorporate nucleotides both by misreading the template and by a primer-template slippage mechanism. The mechanistic and biological implications of these results are discussed.