1996
Winners
Special Achievement
Albert Lasker Award
for Special Achievement in Medical Science
Paul Zamecnik talks with Richard M. Cohen, former senior producer, CBS Evening News, and Mahlon Hoagland, M.D., former scientific director of the Worcester Institute for Experiential Biology, about his life in medicine.
Zamecnik: I was born in Cleveland, Ohio and came to college at Dartmouth just to get a change of scenery from the Midwest, so I found myself more interested in basic science than in clinical medicine. But there was a gap, more of a gap than of course there is now, between clinical medicine and its underpinnings, and I thought that was a better way to spend one's life beginning at that time than trying to butt one's head against the wall in treatment of diseases which had no therapy at all.
I wouldn't trade this for a life in clinical medicine because here you are trying to add to the sum total of knowledge and there you are applying a very useful way that already is known.
Cohen: Did you ever do clinical work?
Zamecnik: Sure. When I had my internship and when I was the resident at the old Huntington Hospital, I was in charge of those patients. I liked seeing the patients but nevertheless, when the time came to move up the ladder and become a resident there, by that time we were married. We saw on the bulletin board an advertisement for a fellowship to do research. So we had $2500 and we went off to Denmark. It turned out to be 1939 in the mid part of August. We took an old freighter from Montreal headed for Bristol, England and it took us about 12 to 15 days to get there.
As we were crossing, the war was approaching. We listened in on the Captain's radio every evening. When we arrived in Bristol, they were having an air raid practice from France. So we thought, "Oh God, let's get to Copenhagen," and we did. We went to the American Consulate there, who said, "Well I really don't know very much about what has happened during the night because the Paris Edition of the Herald Tribune hasn't arrived yet." And I said, "Well, how about the Danish newspapers?" He said, "Oh I don't read Danish." I thought that was a little odd. And we found that the American Consulate was full of people speaking a foreign tongue we didn't understand. They were Poles who would come over in small boats from Gdynla the night before, when the invasion had started. So we stayed and we had a very nice year, and I would say that that year was the one which helped determine that we liked science. If only we could make a go of it better than practicing medicine.
Well, I liked people and I enjoyed being in the clinic with them. So when April 9, 1940 came along, we were living on the top floor of an old Danish building, a stone building, and we could hear planes flying over us. We said, "These are German planes. The Dane's won't like this."
Cohen: You have talked about a couple of moments when it sounds like you realized that research was your future. One was at that hospital. And then secondly....
Zamecnik: At Carlsburg.
Cohen: Tell me the evolution of that decision.
Zamecnik: Well, I found it interesting at the Huntington Hospital that people were studying cancer as a problem of growth—that is, an aberration of the regulation of growth, and that one of the objects of study was a rat liver.
Hoagland: Paul was a remarkable person to me. One of the most striking things about him is that he created a laboratory atmosphere that was very informal, very relaxed, very good fun, and with very little pressure of competition in the laboratory. He also was strikingly generous in attributing, in recognizing the contributions of other people to the areas that he was working with, and urged his associates to be generous in their acknowledgment of the work of other people. I think his whole attitude contributed significantly to an openness and sharing which, in turn, contributed to the success of the laboratory.
Zamecnik: At Carlsburg, I met people in such a tiny country who were eminent scientists—for instance, Niels Bohr. We met him and knew his sons and had dinner at his house and showed films there. And there was another—the father of radioactivity, called George de Hevesy. He was also later a Nobel Prize winner. There was the Director of the Carlsburg Laboratory itself, this young multi-gifted Danish fellow, Per Lindstrom Lang, who was a good mathematician, physical chemist, storyteller and painter. When I first came into the laboratory, he was wearing a long white coat, and there were streaks under his arm—all in red under one arm, just on one arm, and I asked him, "Why are those streaks under the arm?" Oh well, he [said he] lives in the house adjoining the laboratory, connected by a little corridor, and he goes back and he paints and he wipes his brush under his arm.
There were people in the tiny country, most of whom had never heard of the American scientists who I knew of, or the American professors of medicine, and that they spent their whole lives in science.
Cohen: So how old were you when you returned to the States from Denmark?
Zamecnik: Oh let's see, about 26.
Cohen: So you are 26 years old, and between Huntington and Denmark you have already chosen a path.
Zamecnik: I should have mentioned to you though, that there was another influence. When I was an intern at University Hospitals in Cleveland, a very fat lady came in. She waddled in and she was out of breath, and they put her in bed and thought, well, we will go easy on her, but we will gradually reduce her in weight. She died a week later. And at the autopsy they didn't find anything—except everywhere they looked, she had too much fat and too little protein, really. And so I wondered, "Okay now, what determines the regulation of how much? How do you make protein anyway?" I asked that question. "How do you make protein?" And I asked the people in medicine at the University Hospitals, "Who is studying protein synthesis?" And they all shook their heads.
There was one paragraph in their biochemistry text books which didn't explain anything. But one fellow had been at the Rockefeller Institute, and he said there is a refugee chemist who has just come over out of the Nazi draft, Hitler's draft, and he is studying protein synthesis. And so I got his name and I went to visit him in 1938. His name was Max Bergman, and he had been studying letter chemistry and protein synthesis. But he had to leave, and he looked at me and said, "We don't take medical people, we take organic chemists here. We want to find out how proteins are put together and how they are taken apart."
Cohen: You talked about your interest in proteins, and I am wondering if there is continuity between that early interest in proteins and your later work?
Zamecnik: Well, it comes about in this way, that there was a funny fellow who turned up at the Mass General called Fritz Lippman. He was a biochemist refugee who turned up in the Department of Surgery at the MGH because he couldn't get anything else, and I was having lunch with him. He was the only biochemist at the MGH, and one day in 1944 he said, "Paul, you don't really think those Bergman enzymes have anything to do with protein synthesis, do you?" I shook my head and said, "Here you are, just a young guy relatively, and you are taking on the great Bergman." But I thought maybe he is right. As soon as the war is over, we will drop what we are doing like a rock, and we will try to find out whether Bergman is right or Lipman is right, and so we continued on that path.
Cohen: But that is a direct road to the research you did later on it.
Zamecnik: It is a direct road to the work we did on protein synthesis. Because we found that in whole cells you needed energy to make protein. And then we said, yeah, but what is going on inside the cell? You have to break it up and then try to reproduce part of it and see what the steps are. So it took nearly 5 years to develop a cell-free system whereby you could add the carbon 14 label amino acid and see if it made its way into protein. It didn't unless you added energy. So we added ATP and nothing happened, but you had to have a continuous source for making ATP energy. And when we did that, we got it. And the whole field broke open then for us and for a lot of other people who looked at it and carried it forward in brilliant ways.
Cohen: Tell us what RNA is and what its function is.
Zamecnik: Well, let me start with DNA. The DNA is a four letter alphabet: A - G - C - T, like those four letters. And they can come in any sequence. Say there are three billion of them in the human genome divided up into chromosomes, and they are the repository for the genetic information, but they stay in a nucleus. Carbon copies are sort of made and sent out into the cytoplasm or down into the provinces, as though the king sits in his castle and has copies made and they are sent out to the construction workers, and RNA is what they send out.
Cohen: So DNA is what you are.
Zamecnik: Yup.
Cohen: Everything you are is in the DNA, but you have got to send the message out to the empire.
Zamecnik: That is it, and you don't send the DNA out: you send cheap copies that are broken down. The DNA is preserved, but you make cheap copies and send this RNA out into the provinces, and then it is converted into protein.
Cohen: So the RNA is a courier that can translate it.
Zamecnik: It is a courier which then translates the message of the gene into that of the protein, and it translates it by way of this little molecule, transfer RNA, which has three prongs which determine where it will sit on the RNA. And on the other end it has an amino acid which is attached to it. There are 20 different transfer RNAs and there are 20 different enzymes which attach the correct amino acid onto a given transfer RNA.
Cohen: So the transfer RNA, in the end, makes us who we are. It is almost carrying the orders from the DNA.
Zamecnik: It carries the orders. That is right. It is the translator who translates Russian into English. It is the interpreter.
Cohen: Was this very exciting for you?
Zamecnik: Oh gosh, it was very exciting.
Cohen: Tell us about the process.
Zamecnik: The first thing was to get a cell-free system so that you have a balloon capsule around all the information that is inside. You have to break it and then take apart various pieces: mitochondria, the ribosomes, the soluble enzymes, and energy producers, and then put them together in different combinations and see what works...using a labeled amino acid as your determinant and precipitating out protein at the end to see if a label gets into it.
Well, we found that you needed several components. First, you needed the amino acid. You needed energy and you needed what became known as ribosomes, the marshaling site where this assembly line took place. We put those together and nothing happened. We thought, gee, there must be some piece missing. So we were looking then for a translation piece. So the concept of messenger RNA was in the air and then there was a young fellow named Nirenberg and a post doc named Metai who came from Germany at the NIH who then pinpointed, or what one would say, "cracked" the genetic code. They showed that actually it is true that one transfer RNA would code for just one amino acid, and so when they found that this poly U coded for perphenazine, that was a crack. And Nirenberg and Metai and Carona, who were very good organic chemists, broke the genetic code, and within five years it was all spelled out.
Cohen: What years are you talking about now?
Zamecnik: 1961 to 1965.
Cohen: What is the utilitarian value of the research that was done on RNA? Where has it taken us?
Zamecnik: It has served as a foundation stone for lots of molecular biology. In particular, most of the antibiotics interfere with protein synthesis, with transcription of the message that is sent by the DNA and gene through RNA to protein. Somewhere along that line, a good number of them block the actual translation of the message itself. So the antibiotic field, although it didn't come out of that work, has benefited enormously, and lots of biotech companies have been spawned due to the availability of that information. I would say that the concept of DNA and RNA and then of protein make up the skeleton of what we know about molecular biology, and the rest of that is filling in and is making it utilitarian.
Cohen: You were a well-educated detective.
Zamecnik: Well, we were serendipitous maybe, and maybe we were too naive not to consider that trying to make a cell-free system which would synthesize protein was too much of a job. It is like putting wax wings on and flying too high, but it worked. Some of our competitors at that level were looking for the question we were trying to answer—the question of whether proteins were made by spot welding energy into them. We were using a simpler system, making a simple peptide. Lipman was trying to do that. But this worked. This complicated system did work.
Hoagland: Paul Zamecnik and I really contributed significantly to understanding how genetic information actually is built into protein molecules, which are essentially us. We are protein molecules. We have learned the sort of fundamental process by which all information is transmitted down the generations and how it is built into each individual at each generation.
Cohen: You were nominated for a Nobel Prize, and a lot of people assumed that you would get it, which you didn't. Was that a pretty big disappointment?
Zamecnik: Well, in the first place I didn't think it would happen. I didn't give it much thought. Somebody called me on the telephone and said, "You have done something exciting and you are being nominated for a big prize," and I said, "I don't know," and then I began to get that there was a false rumor that came over the Associated Press the night before the prize was to be given. I got telephone calls from various places, and we brought up some champagne, but I didn't shake anybody's hand. And I knew that other people—for instance, Hans Krebs—had a leak occurring there, too, and he didn't get it until years later somehow. Well anyway, the next morning the prize went to Conrad Block in London for work on cholesterol synthesis, and that was very nice work. Well, I don't know. I just thought, "I will keep going." And then people said, "Oh don't worry about it...next year," and so on.
Hoagland: Personally I feel it was a major oversight. I don't mind saying this of the Nobel Committee. His contributions are just enormous compared to a great many people who did get the prize.
Cohen: So let's talk about antisense. Explain it to me. It is one strand of DNA, right?
Zamecnik: It is the surrogate for DNA. Initially we chose a virus. It was known as the Rous sarcoma virus, which is an RNA virus, but we will call it genetic. It has a single genetic strand which is 5,000 nucleotides long. Instead of being 3 billion, this is 5,000, and hey if we can sequence part of this 5,000, we will find out how it does its trick.
So we prepared enough of the RNA of the Rous sarcoma virus to make it feasible to try to sequence it. In other words, to find out what the sequential array of genetic layers was. And after a couple of very talented people in our laboratory—one named David Schwartz and another Lee White—had worked for three years, they found 21 letters at one end of this virus. It is like a long strand and has one end, and then the other end. And at the so-called three prime end—the far end—they found 21 letters inside a tail. We won't even talk about the tail, but the letters didn't amount to anything. Twenty-one took three years.
And then we found that there were some people across the river at Harvard who we didn't know—Maxim and Gilbert—who had a new revolutionary way of sequencing DNA. They hadn't published it, but they invited us to come over and talk to them. Weiss and Schwartz went over and talked to Maxim and Gilbert, and they came back and their heads were hanging down. They said, "My God, we have been working three years and we got 21, and they are working on the same virus that we are—the Rous sarcoma virus—but at the other end, the far prime end. And they have only been working on it 6 weeks and they have 101 residents. Oh, God, there must be some other business we can go into."
But then I said, "There is one funny thing though: their end of the virus is exactly the same as our end." Well, that is an oddity and in the same sort of polarity. Now there had been known by electron microscopy that it appeared that this virus circularized before it replicated—made a copy of itself—and so this provided an explanation as to how it would circularize. Because this RNA was the substance the virus was copied back into DNA, by an enzyme known as a reverse transcriptase, and that had been found just a few years before in a sort of critical description by Cadman and Baltimore to be the activity of an enzyme called the reverse transcriptase.
Now the central dogma was that DNA makes RNA, makes protein, but it doesn't go backwards. But here it was going backwards from RNA to DNA. The arrow was going up and they were making DNA which then made its way into the host protein, I mean the host DNA, and then the new virus was made down in the usual way. So you could get reverse transcriptase and make your RNA from this Rous sarcoma virus, copy it and make a piece of DNA out of it.
Cohen: Am I correct in saying that the value in that manipulation is that people with genetic diseases—you can break that link?
Zamecnik: Well, there is one part of genetics that hasn't really been cracked, and that is: How do you replace a piece of a damaged gene with a good one? There have been reports and special circumstances that it can be done, but in general, you can't do it. And that will be the next big break.
Hoagland: One of the ways he is going to be remembered is that I have never known in science an individual who is so totally committed to science. Paul has always stayed in the laboratory working at the bench. Not only has he been working at the bench, but he has been remarkably successful at it.
Cohen: When you look back, are you pleased with your life's work?
Zamecnik: Oh, I think it was a nice lucky break. At Dartmouth, there one used the analogy of Okham's razor. Now you don't make...things any more complicated than you have to. That is generally wrong in biology. Things are always more complicated.