A DUI indicates that you are a higher risk as a driver, and have a greater chance of having an accident while driving or possibly having a fatal car crash.
Every life insurance carrier has their own rules for the types of risks that they are currently willing to accept for life insurance, and also their own weighting method for the risks that they are willing to accept. So, if you are accepted with a DUI, you will pay more than the average driver, because you present a greater risk for death of an insured.
However, if it has been more than 5 years since your DUI, you may find it easier to qualify for life insurance coverage at a reasonable rate.
If you are turned down for life insurance by several insurers you may want to consider looking into high risk life insurance which is coverage for people who present a higher risk to the insurance company due to their age, health, driving record, etc.